Improving systemic therapy selection for inflammatory skin diseases: A clinical need survey.

Background: Empirical decisions to select therapies for psoriasis (PSO) and atopic dermatitis (AD) can lead to delays in disease control and increased health care costs. However, routine molecular testing for AD and PSO are lacking. Objective: To examine (1) how clinicians choose systemic therapies for patients with PSO and AD without molecular testing and (2) to determine how often the current approach leads to patients switching medications. Methods: A 20-question survey designed to assess clinician strategies for systemic treatment of AD and PSO was made available to attendees of a national dermatology conference in 2022. Results: Clinicians participating in the survey (265/414, 64% response rate) ranked "reported efficacy" as the most important factor governing treatment choice (P < .001). However, 62% (165/265) of clinicians estimated that 2 or more systemic medications were typically required to achieve efficacy. Over 90% (239/265) of respondents would or would likely find a molecular test to guide therapeutic selection useful. Limitations: To facilitate ease of recall, questions focused on systemic therapies as a whole and not individual therapies. Conclusion: Clinicians want a molecular test to help determine the most efficacious drug for individual patients.

Altered myocardial lipid regulation in junctophilin-2-associated familial cardiomyopathies.

Myocardial lipid metabolism is critical to normal heart function, whereas altered lipid regulation has been linked to cardiac diseases including cardiomyopathies. Genetic variants in the JPH2 gene can cause hypertrophic cardiomyopathy (HCM) and, in some cases, dilated cardiomyopathy (DCM). In this study, we tested the hypothesis that JPH2 variants identified in patients with HCM and DCM, respectively, cause distinct alterations in myocardial lipid profiles. Echocardiography revealed clinically significant cardiac dysfunction in both knock-in mouse models of cardiomyopathy. Unbiased myocardial lipidomic analysis demonstrated significantly reduced levels of total unsaturated fatty acids, ceramides, and various phospholipids in both mice with HCM and DCM, suggesting a common metabolic alteration in both models. On the contrary, significantly increased di- and triglycerides, and decreased co-enzyme were only found in mice with HCM. Moreover, mice with DCM uniquely exhibited elevated levels of cholesterol ester. Further in-depth analysis revealed significantly altered metabolites from all the lipid classes with either similar or opposing trends in JPH2 mutant mice with HCM or DCM. Together, these studies revealed, for the first time, unique alterations in the cardiac lipid composition-including distinct increases in neutral lipids and decreases in polar membrane lipids-in mice with HCM and DCM were caused by distinct JPH2 variants. These studies may aid the development of novel biomarkers or therapeutics for these inherited disorders.

Clinical Utility of the 31-Gene Expression Profile Test on the Management of Cutaneous Melanoma by Nurse Practitioners and Physician Assistants.

Objective: The 31-gene expression profile (31-GEP) can predict the risk of recurrence and metastasis in cutaneous melanoma (CM). We assessed the viewpoints and use of 31-GEP testing by physician assistants (PAs) and nurse practitioners (NPs) for patients with CM. Methods: NPs and PAs (n = 369) completed an 18-question online survey about their viewpoints and use of the 31-GEP risk-stratification test. Results: Most practitioners (n = 334, 90.5%) felt prognostic testing improved patient care and would recommend the 31-GEP to a colleague (n = 333, 90.2%) or a friend or family member (n = 289, 78.3%) who was diagnosed with CM. The 31-GEP test was used by 176 respondents in the preceding 12 months (53%). Among users of the 31-GEP test, 78% stated that the results would impact follow-up schedule and referral, 66% overall treatment decisions, 62% sentinel lymph node biopsy recommendations, and 50% surveillance imaging. In thin tumors (≤ 1 mm), 82% of 31-GEP users and 44% of nonusers stated that the 31-GEP results would impact their treatment plan decisions. Conclusion: The 31-GEP test significantly impacts treatment plans in CM, particularly for thin and stage I melanomas. Importantly, even nonusers stated that 31-GEP test results would impact treatment plans as well as recommendations to a friend or family member.

Prolonged ß-adrenergic stimulation disperses ryanodine receptor clusters in cardiomyocytes and has implications for heart failure.

Ryanodine receptors (RyRs) exhibit dynamic arrangements in cardiomyocytes, and we previously showed that 'dispersion' of RyR clusters disrupts Ca2+ homeostasis during heart failure (HF) (Kolstad et al., eLife, 2018). Here, we investigated whether prolonged ß-adrenergic stimulation, a hallmark of HF, promotes RyR cluster dispersion and examined the underlying mechanisms. We observed that treatment of healthy rat cardiomyocytes with isoproterenol for 1 hr triggered progressive fragmentation of RyR clusters. Pharmacological inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) reversed these effects, while cluster dispersion was reproduced by specific activation of CaMKII, and in mice with constitutively active Ser2814-RyR. A similar role of protein kinase A (PKA) in promoting RyR cluster fragmentation was established by employing PKA activation or inhibition. Progressive cluster dispersion was linked to declining Ca2+ spark fidelity and magnitude, and slowed release kinetics from Ca2+ propagation between more numerous RyR clusters. In healthy cells, this served to dampen the stimulatory actions of ß-adrenergic stimulation over the longer term and protect against pro-arrhythmic Ca2+ waves. However, during HF, RyR dispersion was linked to impaired Ca2+ release. Thus, RyR localization and function are intimately linked via channel phosphorylation by both CaMKII and PKA, which, while finely tuned in healthy cardiomyocytes, underlies impaired cardiac function during pathology.

Optimizing treatment approaches for patients with cutaneous melanoma by integrating clinical and pathologic features with the 31-gene expression profile test.

BACKGROUND: Many patients with low-stage cutaneous melanoma will experience tumor recurrence, metastasis, or death, and many higher staged patients will not. OBJECTIVE: To develop an algorithm by integrating the 31-gene expression profile test with clinicopathologic data for an optimized, personalized risk of recurrence (integrated 31 risk of recurrence [i31-ROR]) or death and use i31-ROR in conjunction with a previously validated algorithm for precise sentinel lymph node positivity risk estimates (i31-SLNB) for optimized treatment plan decisions. METHODS: Cox regression models for ROR were developed (n = 1581) and independently validated (n = 523) on a cohort with stage I-III melanoma. Using National Comprehensive Cancer Network cut points, i31-ROR performance was evaluated using the midpoint survival rates between patients with stage IIA and stage IIB disease as a risk threshold. RESULTS: Patients with a low-risk i31-ROR result had significantly higher 5-year recurrence-free survival (91% vs 45%, P < .001), distant metastasis-free survival (95% vs 53%, P < .001), and melanoma-specific survival (98% vs 73%, P < .001) than patients with a high-risk i31-ROR result. A combined i31-SLNB/ROR analysis identified 44% of patients who could forego sentinel lymph node biopsy while maintaining high survival rates (>98%) or were restratified as being at a higher or lower risk of recurrence or death. LIMITATIONS: Multicenter, retrospective study. CONCLUSION: Integrating clinicopathologic features with the 31-GEP optimizes patient risk stratification compared to clinicopathologic features alone.

Improved cutaneous melanoma survival stratification through integration of 31-gene expression profile testing with the American Joint Committee on Cancer 8th Edition Staging.

Cutaneous melanoma (CM) survival is assessed using averaged data from the American Joint Committee on Cancer 8th edition (AJCC8). However, subsets of AJCC8 stages I-III have better or worse survival than the predicted average value. The objective of this study was to determine if the 31-gene expression profile (31-GEP) test for CM can further risk-stratify melanoma-specific mortality within each AJCC8 stage. This retrospective multicenter study of 901 archival CM samples obtained from patients with stages I-III CM assessed 31-GEP test predictions of 5-year melanoma-specific survival (MSS) using Kaplan-Meier and Cox proportional hazards. In stage I-III CM population, patients with a Class 2B result had a lower 5-year MSS (77.8%) than patients with a Class 1A result (98.7%) and log-rank testing demonstrated significant stratification of MSS [χ2 (2df, n = 901) = 99.7, P < 0.001). Within each stage, 31-GEP data provided additional risk stratification, including in stage I [χ2 (2df, n = 415) = 11.3, P = 0.004]. Cox regression multivariable analysis showed that the 31-GEP test was a significant predictor of melanoma-specific mortality (MSM) in patients with stage I-III CM [hazard ratio: 6.44 (95% confidence interval: 2.61-15.85), P < 0.001]. This retrospective study focuses on Class 1A versus Class 2B results. Intermediate results (Class 1B/2A) comprised 21.6% of cases with survival rates between Class 1A and 2B, and similar to 5-year MSS AJCC stage values. Data from the 31-GEP test significantly differentiates MSM into lower (Class 1A) and higher risk (Class 2B) groups within each AJCC8 stage. Incorporating 31-GEP results into AJCC8 survival calculations has the potential to more precisely assess survival and enhance management guidance.

Using a 31-Gene Expression Profile Test to Stratify Patients with Stage I-II Cutaneous Melanoma According to Recurrence Risk: Update to a Prospective, Multicenter Study.

BACKGROUND: Fifteen to forty percent of patients with localized cutaneous melanoma (CM) (stages I-II) will experience disease relapse. The 31-gene expression profile (31-GEP) uses gene expression data from the primary tumor in conjunction with clinicopathologic features to refine patient prognosis. The study's objective was to evaluate 31-GEP risk stratification for disease-free survival (DFS) in a previously published cohort with longer follow-up. METHODS: Patients with stage IB-II CM (n = 86) were prospectively tested with the 31-GEP. Follow-up time increased from 2.2 to 3.9 years. Patient outcomes were compared using Kaplan-Meier and Cox regression analysis. RESULTS: A Class 2B result was a significant predictor of 3-year DFS (hazard ratio (HR) 8.4, p = 0.008) in univariate analysis. The 31-GEP significantly stratified patients by risk of relapse (p = 0.005). A Class 2B result was associated with a lower 3-year DFS (75.0%) than a Class 1A result (100%). The 31-GEP had a high sensitivity (77.8%) and negative predictive value (95.0%). CONCLUSIONS: The 31-GEP is a significant predictor of disease relapse in patients with stage IB-II melanoma and accurately stratified patients by risk of relapse.

Expanded evidence that the 31-gene expression profile test provides clinical utility for melanoma management in a multicenter study.

OBJECTIVE: National Comprehensive Cancer Network (NCCN) guidelines for cutaneous melanoma (CM) recommend physicians consider increased surveillance for patients who typically have lower melanoma survival rates (stages IIB-IV as determined by the American Joint Committee on Cancer (AJCC), 8th edition). However, up to 15% of patients identified as having a low recurrence risk (stages I-IIA) experience disease recurrence, and some patients identified as having a high recurrence risk will not experience any recurrence. The 31-gene expression profile test (31-GEP) stratifies patient recurrence risk into low (Class 1) and high (Class 2) and has demonstrated risk-appropriate impact on disease management and clinical decisions. METHODS: Five-year plans for lab work, frequency of clinical visits, and imaging pre- and post-31-GEP test results were assessed for a cohort of 509 stage I-III patients following an interim subset analysis of 247 patients. RESULTS: After receiving 31-GEP results, 50.6% of patients had a change in management plans in at least one of the following categories-clinical visits, lab work, or surveillance imaging. The changes aligned with the risk predicted by the 31-GEP for 76.1% of patients with a Class 1 result and 78.7% of patients with a Class 2 result. A Class 1 31-GEP result was associated with changes toward low-intensity management recommendations, while a Class 2 result was associated with changes toward high-intensity management recommendations. CONCLUSION: The 31-GEP can stratify patient recurrence risk in patients with CM, and clinicians understand and apply the prognostic ability of the 31-GEP test to alter patient management in risk-appropriate directions.

When caught early, cancer of the skin can usually be removed, and patients have excellent chances of survival. However, some patients will have their cancer come back or spread to a new location in their body.The 31-gene expression profile (GEP) test measures the expression levels of 31 genes from an individual patient's tumor. A proprietary formula uses this information to identify the risk of recurrence or spread as low risk (Class 1) or high risk (Class 2). Cancers with low-risk 31-GEP scores have a lower chance of cancer recurrence or spread than patients with a high-risk score.In this study, we wanted to determine if doctors treated patients with low-risk scores differently from patients with high-risk scores. We found that doctors changed approximately half of patient treatment plans (doctor visits, lab work, or imaging to see if the cancer has come back) after learning the 31-GEP test results. Doctors usually planned less frequent follow-up visits for Class 1 results and more frequent follow up for Class 2 results.This study found doctors understand and make changes to their treatment plans based on the patient's 31-GEP test result.

Development and validation of a nomogram incorporating gene expression profiling and clinical factors for accurate prediction of metastasis in patients with cutaneous melanoma following Mohs micrographic surgery.

BACKGROUND: There is a need to improve prognostic accuracy for patients with cutaneous melanoma. A 31-gene expression profile (31-GEP) test uses the molecular biology of primary tumors to identify individual patient metastatic risk. OBJECTIVE: Develop a nomogram incorporating 31-GEP with relevant clinical factors to improve prognostic accuracy. METHODS: In an IRB-approved study, 1124 patients from 9 Mohs micrographic surgery centers were prospectively enrolled, treated with Mohs micrographic surgery, and underwent 31-GEP testing. Data from 684 of those patients with at least 1-year follow-up or a metastatic event were included in nomogram development to predict metastatic risk. RESULTS: Logistic regression modeling of 31-GEP results and T stage provided the simplest nomogram with the lowest Bayesian information criteria score. Validation in an archival cohort (n = 901) demonstrated a significant linear correlation between observed and nomogram-predicted risk of metastasis. The resulting nomogram more accurately predicts the risk for cutaneous melanoma metastasis than T stage or 31-GEP alone. LIMITATIONS: The patient population is representative of Mohs micrographic surgery centers. Sentinel lymph node biopsy was not performed for most patients and could not be used in the nomogram. CONCLUSIONS: Integration of 31-GEP and T stage can gain clinically useful prognostic information from data obtained noninvasively.

Integrating 31-Gene Expression Profiling With Clinicopathologic Features to Optimize Cutaneous Melanoma Sentinel Lymph Node Metastasis Prediction.

National guidelines recommend sentinel lymph node biopsy (SLNB) be offered to patients with > 10% likelihood of sentinel lymph node (SLN) positivity. On the other hand, guidelines do not recommend SLNB for patients with T1a tumors without high-risk features who have < 5% likelihood of a positive SLN. However, the decision to perform SLNB is less certain for patients with higher-risk T1 melanomas in which a positive node is expected 5%-10% of the time. We hypothesized that integrating clinicopathologic features with the 31-gene expression profile (31-GEP) score using advanced artificial intelligence techniques would provide more precise SLN risk prediction. METHODS: An integrated 31-GEP (i31-GEP) neural network algorithm incorporating clinicopathologic features with the continuous 31-GEP score was developed using a previously reported patient cohort (n = 1,398) and validated using an independent cohort (n = 1,674). RESULTS: Compared with other covariates in the i31-GEP, the continuous 31-GEP score had the largest likelihood ratio (G2 = 91.3, P < .001) for predicting SLN positivity. The i31-GEP demonstrated high concordance between predicted and observed SLN positivity rates (linear regression slope = 0.999). The i31-GEP increased the percentage of patients with T1-T4 tumors predicted to have < 5% SLN-positive likelihood from 8.5% to 27.7% with a negative predictive value of 98%. Importantly, for patients with T1 tumors originally classified with a likelihood of SLN positivity of 5%-10%, the i31-GEP reclassified 63% of cases as having < 5% or > 10% likelihood of positive SLN, for a more precise, personalized, and clinically actionable SLN-positive likelihood estimate. CONCLUSION: These data suggest the i31-GEP could reduce the number of SLNBs performed by identifying patients with likelihood under the 5% threshold for performance of SLNB and improve the yield of positive SLNBs by identifying patients more likely to have a positive SLNB.

The 31-gene expression profile stratifies recurrence and metastasis risk in patients with cutaneous melanoma.

Aim: Sentinel node biopsy is a prognostic indicator of melanoma recurrence. We hypothesized that adding the primary melanoma molecular signature from the 31-gene expression profile (31-GEP) test could refine the risk of recurrence prognosis for patients with stage I-III melanoma. Materials & methods: Four hundred thirty-eight patients with stage I-III melanoma consecutively tested with the 31-GEP were retrospectively analyzed. The 31-GEP stratified patients as low-risk (Class 1A), intermediate-risk (Class 1B/2A) or high risk (Class 2B) of recurrence or metastasis. Results: The 31-GEP significantly stratified patient risk for recurrence-free survival (p < 0.001), distant metastasis-free survival (p < 0.001) and melanoma-specific survival (p < 0.001) and was a significant, independent predictor of metastatic recurrence (hazard ratio: 5.38; p = 0.014). Conclusion: The 31-GEP improves prognostic accuracy in stage I-III melanoma.

Lay abstract Cutaneous melanoma is a type of skin tumor affecting 100,000 new patients each year. Even with the best tools available today, knowing which patients will die from their cancer can be challenging. Using individual tumors from over 400 patients, we analyzed the expression of 31 genes from each tumor. Doing this helped us split the patients into groups who are more or less likely to die from their tumor. By combining this technique with current medical practices and guidelines, we hope to help identify which patients may or may not benefit from more intense therapies.

Efficacy of RyR2 inhibitor EL20 in induced pluripotent stem cell-derived cardiomyocytes from a patient with catecholaminergic polymorphic ventricular tachycardia.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited cardiac arrhythmia syndrome that often leads to sudden cardiac death. The most common form of CPVT is caused by autosomal-dominant variants in the cardiac ryanodine receptor type-2 (RYR2) gene. Mutations in RYR2 promote calcium (Ca2+ ) leak from the sarcoplasmic reticulum (SR), triggering lethal arrhythmias. Recently, it was demonstrated that tetracaine derivative EL20 specifically inhibits mutant RyR2, normalizes Ca2+ handling and suppresses arrhythmias in a CPVT mouse model. The objective of this study was to determine whether EL20 normalizes SR Ca2+ handling and arrhythmic events in induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from a CPVT patient. Blood samples from a child carrying RyR2 variant RyR2 variant Arg-176-Glu (R176Q) and a mutation-negative relative were reprogrammed into iPSCs using a Sendai virus system. iPSC-CMs were derived using the StemdiffTM kit. Confocal Ca2+ imaging was used to quantify RyR2 activity in the absence and presence of EL20. iPSC-CMs harbouring the R176Q variant demonstrated spontaneous SR Ca2+ release events, whereas administration of EL20 diminished these abnormal events at low nanomolar concentrations (IC50  = 82 nM). Importantly, treatment with EL20 did not have any adverse effects on systolic Ca2+ handling in control iPSC-CMs. Our results show for the first time that tetracaine derivative EL20 normalized SR Ca2+ handling and suppresses arrhythmogenic activity in iPSC-CMs derived from a CPVT patient. Hence, this study confirms that this RyR2-inhibitor represents a promising therapeutic candidate for treatment of CPVT.

Long-Term Outcomes in a Multicenter, Prospective Cohort Evaluating the Prognostic 31-Gene Expression Profile for Cutaneous Melanoma.

PURPOSE: Current guidelines for postoperative management of patients with stage I-IIA cutaneous melanoma (CM) do not recommend routine cross-sectional imaging, yet many of these patients develop metastases. Methods that complement American Joint Committee on Cancer (AJCC) staging are needed to improve identification and treatment of these patients. A 31-gene expression profile (31-GEP) test predicts metastatic risk as low (class 1) or high (class 2). Prospective analysis of CM outcomes was performed to test the hypotheses that the 31-GEP provides prognostic value for patients with stage I-III CM, and that patients with stage I-IIA melanoma and class 2 31-GEP results have metastatic risk similar to patients for whom surveillance is recommended. MATERIALS AND METHODS: Two multicenter registry studies, INTEGRATE (ClinicalTrials.gov identifier:NCT02355574) and EXPAND (ClinicalTrials.gov identifier:NCT02355587), were initiated under institutional review board approval, and 323 patients with stage I-III CM and median follow-up time of 3.2 years met inclusion criteria. Primary end points were 3-year recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and overall survival (OS). RESULTS: The 31-GEP was significant for RFS, DMFS, and OS in a univariate analysis and was a significant, independent predictor of RFS, DMFS, and OS in a multivariable analysis. GEP class 2 results were significantly associated with lower 3-year RFS, DMFS, and OS in all patients and those with stage I-IIA disease. Patients with stage I-IIA CM and a class 2 result had recurrence, distant metastasis, and death rates similar to patients with stage IIB-III CM. Combining 31-GEP results and AJCC staging enhanced sensitivity over each approach alone. CONCLUSION: These data provide a rationale for using the 31-GEP along with AJCC staging, and suggest that patients with stage I-IIA CM and a class 2 31-GEP signature may be candidates for more intense follow-up.

Risk Stratification of Patients with Stage I Cutaneous Melanoma Using 31-Gene Expression Profiling.

BACKGROUND: While patients with localized cutaneous melanoma (CM) generally have good five-year melanoma-specific survival rates, identifying patients with localized disease at a high risk of recurrence could allow them access to additional follow-up or surveillance. OBJECTIVE: We sought to examine the prognostic value of the 31-gene expression profile (31-GEP) test for the risk of recurrence in stage I CM patients according to 31-GEP main class (low risk: Class 1 vs. high-risk: Class 2) and the lowest and highest risk 31-GEP subclasses (Class 1A vs. Class 2B). METHODS: Data from a previously described meta-analysis detailing the 31-GEP results for patients with stage I CM (N = 623) were re-analyzed to determine 31-GEP accuracy. RESULTS: Patients with stage I CM and a Class 1 31-GEP result were less likely to have a recurrence (15/556; 2.7% vs. 6/67; 9.0%; p=0.018) than patients with a Class 2 result and had a higher five-year recurrence-free survival (RFS) (96% vs. 85%). Patients with a Class 2 result were 2.8 times as likely to experience a recurrence (positive likelihood ratio: 2.82; 95% confidence interval: 1.38-5.77). In a subset of patients with stage I CM stratified further into 31-GEP subclasses (n = 206), patients with a Class 1A result had a higher five-year RFS than those with a Class 2B result (98% vs. 73%). Patients with a Class 2B result were also 6.5 times as likely to experience a recurrence (positive likelihood ratio: 6.45; 95% confidence interval: 2.44-17.00) than those with a Class 1A result, and the 31-GEP had a negative predictive value of 96.3% (95% confidence interval: 92.3%-98.4%). CONCLUSION: The 31-GEP test significantly differentiates between low and high recurrence risk in patients with stage I CM.

SPEG: a key regulator of cardiac calcium homeostasis.

Proper cardiac Ca2+ homeostasis is essential for normal excitation-contraction coupling. Perturbations in cardiac Ca2+ handling through altered kinase activity has been implicated in altered cardiac contractility and arrhythmogenesis. Thus, a better understanding of cardiac Ca2+ handling regulation is vital for a better understanding of various human disease processes. 'Striated muscle preferentially expressed protein kinase' (SPEG) is a member of the myosin light chain kinase family that is key for normal cardiac function. Work within the last 5 years has revealed that SPEG has a crucial role in maintaining normal cardiac Ca2+ handling through maintenance of transverse tubule formation and phosphorylation of junctional membrane complex proteins. Additionally, SPEG has been causally impacted in human genetic diseases such as centronuclear myopathy and dilated cardiomyopathy as well as in common acquired cardiovascular disease such as heart failure and atrial fibrillation. Given the rapidly emerging role of SPEG as a key cardiac Ca2+ regulator, we here present this review in order to summarize recent findings regarding the mechanisms of SPEG regulation of cardiac excitation-contraction coupling in both physiology and human disease. A better understanding of the roles of SPEG will be important for a more complete comprehension of cardiac Ca2+ regulation in physiology and disease.

Loss of SPEG Inhibitory Phosphorylation of Ryanodine Receptor Type-2 Promotes Atrial Fibrillation.

BACKGROUND: Enhanced diastolic calcium (Ca2+) release through ryanodine receptor type-2 (RyR2) has been implicated in atrial fibrillation (AF) promotion. Diastolic sarcoplasmic reticulum Ca2+ leak is caused by increased RyR2 phosphorylation by PKA (protein kinase A) or CaMKII (Ca2+/calmodulin-dependent kinase-II) phosphorylation, or less dephosphorylation by protein phosphatases. However, considerable controversy remains regarding the molecular mechanisms underlying altered RyR2 function in AF. We thus aimed to determine the role of SPEG (striated muscle preferentially expressed protein kinase), a novel regulator of RyR2 phosphorylation, in AF pathogenesis. METHODS: Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca2+ leak in atrial cardiomyocytes was assessed using confocal Ca2+ imaging. Phosphoproteomics studies and Western blotting were used to measure RyR2 phosphorylation. To test the effects of RyR2-S2367 phosphorylation, knockin mice with an inactivated S2367 phosphorylation site (S2367A) and a constitutively activated S2367 residue (S2367D) were generated by using CRISPR-Cas9. RESULTS: Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca2+ spark frequency in atrial cardiomyocytes with Ca2+ imaging, establishing a causal role for decreased SPEG in AF pathogenesis. Phosphoproteomics in hearts from SPEG cardiomyocyte knockout mice identified RyR2-S2367 as a novel kinase substrate of SPEG. Western blotting demonstrated that RyR2-S2367 phosphorylation was also decreased in patients with paroxysmal AF. RyR2-S2367A mice exhibited an increased susceptibility to pacing-induced AF, and aberrant atrial sarcoplasmic reticulum Ca2+ leak, as well. In contrast, RyR2-S2367D mice were resistant to pacing-induced AF. CONCLUSIONS: Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca2+ release. Reduced SPEG levels and RyR2-S2367 phosphorylation typified patients with paroxysmal AF. Studies in S2367 knockin mouse models showed a causal relationship between reduced S2367 phosphorylation and AF susceptibility. Thus, modulating SPEG activity and phosphorylation levels of the novel S2367 site on RyR2 may represent a novel target for AF treatment.

Nuclear localization of a novel calpain-2 mediated junctophilin-2 C-terminal cleavage peptide promotes cardiomyocyte remodeling.

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Patients with HF exhibit a loss of junctophilin-2 (JPH2), a structural protein critical in forming junctional membrane complexes in which excitation-contraction takes place. Several mechanisms have been proposed to mediate the loss of JPH2, one being cleavage by the calcium-dependent protease calpain. The downstream mechanisms underlying HF progression after JPH2 cleavage are presently poorly understood. In this study, we used Labcas to bioinformatically predict putative calpain cleavage sites on JPH2. We identified a cleavage site that produces a novel C-terminal JPH2 peptide (JPH2-CTP) using several domain-specific antibodies. Western blotting revealed elevated JPH2-CTP levels in hearts of patients and mice with HF, corresponding to increased levels of calpain-2. Moreover, immunocytochemistry demonstrated nuclear localization of JPH2-CTP within ventricular myocytes isolated from a murine model of pressure overload-induced HF as well as rat ventricular myocytes treated with isoproterenol. Nuclear localization of JPH2-CTP and cellular remodeling were abrogated by a genetic mutation of the nuclear localization sequence within JPH2-CTP. Taken together, our studies identified a novel C-terminal fragment of JPH2 (JPH2-CTP) generated by calpain-2 mediated cleavage which localizes within the cardiomyocyte nucleus during HF. Blocking nuclear localization of JPH2-CTP protects cardiomyocytes from isoproterenol-induced hypertrophy in vitro. Future in vivo studies of the nuclear role of JPH2-CTP may reveal a causal association with adverse remodeling during HF and establish CTP as a therapeutic target.

Loss of Protein Phosphatase 1 Regulatory Subunit PPP1R3A Promotes Atrial Fibrillation.

BACKGROUND: Abnormal calcium (Ca2+) release from the sarcoplasmic reticulum (SR) contributes to the pathogenesis of atrial fibrillation (AF). Increased phosphorylation of 2 proteins essential for normal SR-Ca2+ cycling, the type-2 ryanodine receptor (RyR2) and phospholamban (PLN), enhances the susceptibility to AF, but the underlying mechanisms remain unclear. Protein phosphatase 1 (PP1) limits steady-state phosphorylation of both RyR2 and PLN. Proteomic analysis uncovered a novel PP1-regulatory subunit (PPP1R3A [PP1 regulatory subunit type 3A]) in the RyR2 macromolecular channel complex that has been previously shown to mediate PP1 targeting to PLN. We tested the hypothesis that reduced PPP1R3A levels contribute to AF pathogenesis by reducing PP1 binding to both RyR2 and PLN. METHODS: Immunoprecipitation, mass spectrometry, and complexome profiling were performed from the atrial tissue of patients with AF and from cardiac lysates of wild-type and Pln-knockout mice. Ppp1r3a-knockout mice were generated by CRISPR-mediated deletion of exons 2 to 3. Ppp1r3a-knockout mice and wild-type littermates were subjected to in vivo programmed electrical stimulation to determine AF susceptibility. Isolated atrial cardiomyocytes were used for Stimulated Emission Depletion superresolution microscopy and confocal Ca2+ imaging. RESULTS: Proteomics identified the PP1-regulatory subunit PPP1R3A as a novel RyR2-binding partner, and coimmunoprecipitation confirmed PPP1R3A binding to RyR2 and PLN. Complexome profiling and Stimulated Emission Depletion imaging revealed that PLN is present in the PPP1R3A-RyR2 interaction, suggesting the existence of a previously unknown SR nanodomain composed of both RyR2 and PLN/sarco/endoplasmic reticulum calcium ATPase-2a macromolecular complexes. This novel RyR2/PLN/sarco/endoplasmic reticulum calcium ATPase-2a complex was also identified in human atria. Genetic ablation of Ppp1r3a in mice impaired binding of PP1 to both RyR2 and PLN. Reduced PP1 targeting was associated with increased phosphorylation of RyR2 and PLN, aberrant SR-Ca2+ release in atrial cardiomyocytes, and enhanced susceptibility to pacing-induced AF. Finally, PPP1R3A was progressively downregulated in the atria of patients with paroxysmal and persistent (chronic) AF. CONCLUSIONS: PPP1R3A is a novel PP1-regulatory subunit within the RyR2 channel complex. Reduced PPP1R3A levels impair PP1 targeting and increase phosphorylation of both RyR2 and PLN. PPP1R3A deficiency promotes abnormal SR-Ca2+ release and increases AF susceptibility in mice. Given that PPP1R3A is downregulated in patients with AF, this regulatory subunit may represent a new target for AF therapeutic strategies.

STAT3: a link between CaMKII-ßIV-spectrin and maladaptive remodeling?

ßIV-Spectrin, along with ankyrin and Ca2+/calmodulin-dependent kinase II (CaMKII), has been shown to form local signaling domains at the intercalated disc, while playing a key role in the regulation of Na+ and K+ channels in cardiomyocytes. In this issue of the JCI, Unudurthi et al. show that under chronic pressure overload conditions, CaMKII activation leads to ßIV-spectrin degradation, resulting in the release of sequestered STAT3 from the intercalated discs. This in turn leads to dysregulation of STAT3-mediated gene transcription, maladaptive remodeling, fibrosis, and decreased cardiac function. Overall, this study presents interesting findings regarding the role of CaMKII and ßIV-spectrin under physiological as well as pathological conditions.

Oxidized CaMKII (Ca2+/Calmodulin-Dependent Protein Kinase II) Is Essential for Ventricular Arrhythmia in a Mouse Model of Duchenne Muscular Dystrophy.

BACKGROUND: Duchenne muscular dystrophy patients are prone to ventricular arrhythmias, which may be caused by abnormal calcium (Ca2+) homeostasis and elevated reactive oxygen species. CaMKII (Ca2+/calmodulin-dependent protein kinase II) is vital for normal Ca2+ homeostasis, but excessive CaMKII activity contributes to abnormal Ca2+ homeostasis and arrhythmias in cardiomyocytes. Reactive oxygen species induce CaMKII to become autonomously active. We hypothesized that genetic inhibition of CaMKII oxidation (ox-CaMKII) in a mouse model of Duchenne muscular dystrophy can alleviate abnormal Ca2+ homeostasis, thus, preventing ventricular arrhythmia. The objective of this study was to test if selective loss of ox-CaMKII affects ventricular arrhythmias in the mdx mouse model of Duchenne muscular dystrophy. METHODS AND RESULTS: 5-(6)-Chloromethyl-2,7-dichlorodihydrofluorescein diacetate staining revealed increased reactive oxygen species production in ventricular myocytes isolated from mdx mice, which coincides with elevated ventricular ox-CaMKII demonstrated by Western blotting. Genetic inhibition of ox-CaMKII by knockin replacement of the regulatory domain methionines with valines (MM-VV [CaMKII M281/282V]) prevented ventricular tachycardia in mdx mice. Confocal calcium imaging of ventricular myocytes isolated from mdx:MM-VV mice revealed normalization of intracellular Ca2+ release events compared with cardiomyocytes from mdx mice. Abnormal action potentials assessed by optical mapping in mdx mice were also alleviated by genetic inhibition of ox-CaMKII. Knockout of the NADPH oxidase regulatory subunit p47 phox normalized elevated ox-CaMKII, repaired intracellular Ca2+ homeostasis, and rescued inducible ventricular arrhythmias in mdx mice. CONCLUSIONS: Inhibition of reactive oxygen species or ox-CaMKII protects against proarrhythmic intracellular Ca2+ handling and prevents ventricular arrhythmia in a mouse model of Duchenne muscular dystrophy.