Anchored PKA synchronizes adrenergic phosphoregulation of cardiac Cav1.2 channels.

Adrenergic modulation of voltage gated Ca2+ currents is a context specific process. In the heart Cav1.2 channels initiate excitation-contraction coupling. This requires PKA phosphorylation of the small GTPase Rad (Ras associated with diabetes) and involves direct phosphorylation of the Cav1.2 α1 subunit at Ser1700. A contributing factor is the proximity of PKA to the channel through association with A-kinase anchoring proteins (AKAPs). Disruption of PKA anchoring by the disruptor peptide AKAP-IS prevents upregulation of Cav1.2 currents in tsA-201 cells. Biochemical analyses demonstrate that Rad does not function as an AKAP. Electrophysiological recording shows that channel mutants lacking phosphorylation sites (Cav1.2 STAA) lose responsivity to the second messenger cAMP. Measurements in cardiomyocytes isolated from Rad-/- mice show that adrenergic activation of Cav1.2 is attenuated but not completely abolished. Whole animal electrocardiography studies reveal that cardiac selective Rad KO mice exhibited higher baseline left ventricular ejection fraction, greater fractional shortening, and increased heart rate as compared to control animals. Yet, each parameter of cardiac function was slightly elevated when Rad-/- mice were treated with the adrenergic agonist isoproterenol. Thus, phosphorylation of Cav1.2 and dissociation of phospho-Rad from the channel are local cAMP responsive events that act in concert to enhance L-type calcium currents. This convergence of local PKA regulatory events at the cardiac L-type calcium channel may permit maximal ß-adrenergic influence on the fight-or-flight response.

Mitochondrial Calcium Signaling Regulates Branched-Chain Amino Acid Catabolism in Fibrolamellar Carcinoma.

Metabolic adaptations in response to changes in energy supply and demand are essential for survival. The mitochondrial calcium uniporter coordinates metabolic homeostasis by regulating TCA cycle activation, mitochondrial fatty acid oxidation and cellular calcium signaling. However, a comprehensive analysis of uniporter-regulated mitochondrial metabolic pathways has remained unexplored. Here, we investigate the metabolic consequences of uniporter loss- and gain-of-function, and identify a key transcriptional regulator that mediates these effects. Using gene expression profiling and proteomic, we find that loss of uniporter function increases the expression of proteins in the branched-chain amino acid (BCAA) catabolism pathway. Activity is further augmented through phosphorylation of the enzyme that catalyzes this pathway's committed step. Conversely, in the liver cancer fibrolamellar carcinoma (FLC)-which we demonstrate to have high mitochondrial calcium levels- expression of BCAA catabolism enzymes is suppressed. We also observe uniporter-dependent suppression of the transcription factor KLF15, a master regulator of liver metabolic gene expression, including those involved in BCAA catabolism. Notably, loss of uniporter activity upregulates KLF15, along with its transcriptional target ornithine transcarbamylase (OTC), a component of the urea cycle, suggesting that uniporter hyperactivation may contribute to the hyperammonemia observed in FLC patients. Collectively, we establish that FLC has increased mitochondrial calcium levels, and identify an important role for mitochondrial calcium signaling in metabolic adaptation through the transcriptional regulation of metabolism.

cAMP signaling: a remarkably regional affair.

Louis Pasteur once famously said 'in the fields of observation chance favors only the prepared mind'. Much of chance is being in the right place at the right time. This is particularly true in the crowded molecular environment of the cell where being in the right place is often more important than timing. Although Brownian motion argues that enzymes will eventually bump into substrates, this probability is greatly enhanced if both molecules reside in the same subcellular compartment. However, activation of cell signaling enzymes often requires the transmission of chemical signals from extracellular stimuli to intracellular sites of action. This review highlights new developments in our understanding of cAMP generation and the 3D utilization of this second messenger inside cells.

Recruitment of BAG2 to DNAJ-PKAc scaffolds promotes cell survival and resistance to drug-induced apoptosis in fibrolamellar carcinoma.

The DNAJ-PKAc fusion kinase is a defining feature of fibrolamellar carcinoma (FLC). FLC tumors are notoriously resistant to standard chemotherapies, with aberrant kinase activity assumed to be a contributing factor. By combining proximity proteomics, biochemical analyses, and live-cell photoactivation microscopy, we demonstrate that DNAJ-PKAc is not constrained by A-kinase anchoring proteins. Consequently, the fusion kinase phosphorylates a unique array of substrates, including proteins involved in translation and the anti-apoptotic factor Bcl-2-associated athanogene 2 (BAG2), a co-chaperone recruited to the fusion kinase through association with Hsp70. Tissue samples from patients with FLC exhibit increased levels of BAG2 in primary and metastatic tumors. Furthermore, drug studies implicate the DNAJ-PKAc/Hsp70/BAG2 axis in potentiating chemotherapeutic resistance. We find that the Bcl-2 inhibitor navitoclax enhances sensitivity to etoposide-induced apoptosis in cells expressing DNAJ-PKAc. Thus, our work indicates BAG2 as a marker for advanced FLC and a chemotherapeutic resistance factor in DNAJ-PKAc signaling scaffolds.

A technology-enabled multi-disciplinary team-based care model for the management of Long COVID and other fatiguing illnesses within a federally qualified health center: protocol for a two-arm, single-blind, pragmatic, quality improvement professional cluster randomized controlled trial.

BACKGROUND: The clinical burden of Long COVID, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), and other post-infectious fatiguing illnesses (PIFI) is increasing. There is a critical need to advance understanding of the effectiveness and sustainability of innovative approaches to clinical care of patients having these conditions. METHODS: We aim to assess the effectiveness of a Long COVID and Fatiguing Illness Recovery Program (LC&FIRP) in a two-arm, single-blind, pragmatic, quality improvement, professional cluster, randomized controlled trial in which 20 consenting clinicians across primary care clinics in a Federally Qualified Health Center system in San Diego, CA, will be randomized at a ratio of 1:1 to either participate in (1) weekly multi-disciplinary team-based case consultation and peer-to-peer sharing of emerging best practices (i.e., teleECHO (Extension for Community Healthcare Outcomes)) with monthly interactive webinars and quarterly short courses or (2) monthly interactive webinars and quarterly short courses alone (a control group); 856 patients will be assigned to participating clinicians (42 patients per clinician). Patient outcomes will be evaluated according to the study arm of their respective clinicians. Quantitative and qualitative outcomes will be measured at 3- and 6-months post-baseline for clinicians and every 3-months post assignment to a participating clinician for patients. The primary patient outcome is change in physical function measured using the Patient-Reported Outcomes Measurement Information System (PROMIS)-29. Analyses of differences in outcomes at both the patient and clinician levels will include a linear mixed model to compare change in outcomes from baseline to each post-baseline assessment between the randomized study arms. A concurrent prospective cohort study will compare the LC&FIRP patient population to the population enrolled in a university health system. Longitudinal data analysis approaches will allow us to examine differences in outcomes between cohorts. DISCUSSION: We hypothesize that weekly teleECHO sessions with monthly interactive webinars and quarterly short courses will significantly improve clinician- and patient-level outcomes compared to the control group. This study will provide much needed evidence on the effectiveness of a technology-enabled multi-disciplinary team-based care model for the management of Long COVID, ME/CFS, and other PIFI within a federally qualified health center. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05167227 . Registered on December 22, 2021.

Recruitment of BAG2 to DNAJ-PKAc scaffolds promotes cell survival and resistance to drug-induced apoptosis in fibrolamellar carcinoma.

The DNAJ-PKAc fusion kinase is a defining feature of the adolescent liver cancer fibrolamellar carcinoma (FLC). A single lesion on chromosome 19 generates this mutant kinase by creating a fused gene encoding the chaperonin binding domain of Hsp40 (DNAJ) in frame with the catalytic core of protein kinase A (PKAc). FLC tumors are notoriously resistant to standard chemotherapies. Aberrant kinase activity is assumed to be a contributing factor. Yet recruitment of binding partners, such as the chaperone Hsp70, implies that the scaffolding function of DNAJ- PKAc may also underlie pathogenesis. By combining proximity proteomics with biochemical analyses and photoactivation live-cell imaging we demonstrate that DNAJ-PKAc is not constrained by A-kinase anchoring proteins. Consequently, the fusion kinase phosphorylates a unique array of substrates. One validated DNAJ-PKAc target is the Bcl-2 associated athanogene 2 (BAG2), a co-chaperone recruited to the fusion kinase through association with Hsp70. Immunoblot and immunohistochemical analyses of FLC patient samples correlate increased levels of BAG2 with advanced disease and metastatic recurrences. BAG2 is linked to Bcl-2, an anti-apoptotic factor that delays cell death. Pharmacological approaches tested if the DNAJ- PKAc/Hsp70/BAG2 axis contributes to chemotherapeutic resistance in AML12 DNAJ-PKAc hepatocyte cell lines using the DNA damaging agent etoposide and the Bcl-2 inhibitor navitoclax. Wildtype AML12 cells were susceptible to each drug alone and in combination. In contrast, AML12 DNAJ-PKAc cells were moderately affected by etoposide, resistant to navitoclax, but markedly susceptible to the drug combination. These studies implicate BAG2 as a biomarker for advanced FLC and a chemotherapeutic resistance factor in DNAJ-PKAc signaling scaffolds.

Classification of Cushing's syndrome PKAc mutants based upon their ability to bind PKI.

Cushing's syndrome is an endocrine disorder caused by excess production of the stress hormone cortisol. Precision medicine strategies have identified single allele mutations within the PRKACA gene that drive adrenal Cushing's syndrome. These mutations promote perturbations in the catalytic core of protein kinase A (PKAc) that impair autoinhibition by regulatory subunits and compartmentalization via recruitment into AKAP signaling islands. PKAcL205R is found in ∼45% of patients, whereas PKAcE31V, PKAcW196R, and L198insW and C199insV insertion mutants are less prevalent. Mass spectrometry, cellular, and biochemical data indicate that Cushing's PKAc variants fall into two categories: those that interact with the heat-stable protein kinase inhibitor PKI, and those that do not. In vitro activity measurements show that wild-type PKAc and W196R activities are strongly inhibited by PKI (IC50 < 1 nM). In contrast, PKAcL205R activity is not blocked by the inhibitor. Immunofluorescent analyses show that the PKI-binding variants wild-type PKAc, E31V, and W196R are excluded from the nucleus and protected against proteolytic processing. Thermal stability measurements reveal that upon co-incubation with PKI and metal-bound nucleotide, the W196R variant tolerates melting temperatures 10°C higher than PKAcL205. Structural modeling maps PKI-interfering mutations to a ∼20 Šdiameter area at the active site of the catalytic domain that interfaces with the pseudosubstrate of PKI. Thus, Cushing's kinases are individually controlled, compartmentalized, and processed through their differential association with PKI.

Oncogenic PKA signaling increases c-MYC protein expression through multiple targetable mechanisms.

Genetic alterations that activate protein kinase A (PKA) are found in many tumor types. Yet, their downstream oncogenic signaling mechanisms are poorly understood. We used global phosphoproteomics and kinase activity profiling to map conserved signaling outputs driven by a range of genetic changes that activate PKA in human cancer. Two signaling networks were identified downstream of PKA: RAS/MAPK components and an Aurora Kinase A (AURKA)/glycogen synthase kinase (GSK3) sub-network with activity toward MYC oncoproteins. Findings were validated in two PKA-dependent cancer models: a novel, patient-derived fibrolamellar carcinoma (FLC) line that expresses a DNAJ-PKAc fusion and a PKA-addicted melanoma model with a mutant type I PKA regulatory subunit. We identify PKA signals that can influence both de novo translation and stability of the proto-oncogene c-MYC. However, the primary mechanism of PKA effects on MYC in our cell models was translation and could be blocked with the eIF4A inhibitor zotatifin. This compound dramatically reduced c-MYC expression and inhibited FLC cell line growth in vitro. Thus, targeting PKA effects on translation is a potential treatment strategy for FLC and other PKA-driven cancers.

Proximity biotinylation to define the local environment of the protein kinase A catalytic subunit in adrenal cells.

Mutant protein kinase A catalytic subunit (PKAc) drives adrenal Cushing's syndrome, though its signaling interactions remain unclear. This protocol details steps to use live-cell proximity labeling to identify subcellular compartments and proteins closely associated with variants of PKAc in human adrenal cells. We include instructions for clonal cell line generation, live biotin labeling of proximal proteins, isolation of biotinylated proteins, and sample processing for proteomic analysis using the biotin ligase miniTurbo with wild-type and mutant PKAc.1,2 For complete details on the use and execution of this protocol, please refer to Omar et al. (2022).3.

Insurance-mandated weight management program completion before bariatric surgery provides no long-term clinical benefit.

BACKGROUND: There is no evidence that insurance-mandated weight loss before bariatric surgery affects outcomes. OBJECTIVE: This retrospective study evaluated the relationship between insurance-mandated weight management program (WMP) completion before primary bariatric surgery and postoperative outcomes. SETTING: Suburban academic medical center. METHODS: Patients who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB, n = 572) or sleeve gastrectomy (SG, n = 484) from 2014 to 2019 were dichotomized to presence (LRYGB n = 431, SG n = 348) or absence (LRYGB n = 141, SG n = 136) of insurance-mandated WMP completion. Primary endpoints included follow-up rate, percent total weight loss (%TWL), and percent excess weight loss (%EWL) through 60 months after surgery. The Mann-Whitney U test compared between-group means with significance at P < .05. RESULTS: Follow-up rate, %TWL, and %EWL were not different (P = NS) up to 60 months postoperation between groups for either surgery. Both LRYGB and SG patients without WMP completion maintained greater %TWL (LRYGB: 34.4 ± 11.1% versus 29.8 ± 11.0%, P = .159; SG: 21.4 ± 10.0% versus 18.2 ± 10.5%, P = .456) and %EWL (LRYGB: 71.3 ± 26.3% versus 67.6 ± 26.5%, P = .618; SG: 49.2 ± 18.8% versus 47.5 ± 28.8%, P = .753) at 36 months after surgery. Secondarily, duration of time to get to surgery was significantly greater among yes-WMP patients (LRYGB: 178 days versus 121 days, P < .001; SG: 169 days versus 95 days, P < .001). CONCLUSION: Insurance-mandated WMP completion before bariatric surgery delays patient access to surgery without improving postoperative weight loss potential and must be abandoned.

Outcomes of Bariatric Surgery With Concomitant Hiatal Hernia Repair Using an Absorbable Tissue Matrix.

BACKGROUND: Hiatal hernias are a common finding in patients who undergo bariatric surgery with an incidence of about 20% of all bariatric patients. Controversy exists on the utility of a biosynthetic tissue matrix (BTM) usage in combination with crural repair. This study was designed to explore the safety and benefits of the use of a BTM during concomitant hiatal hernia repair with bariatric surgical procedures. METHODS: This was a retrospective chart review of bariatric surgical patients who underwent a concomitant hiatal hernia repair at a single practice at a tertiary academic medical center from January 2014 to February 2019. RESULTS: A total of 420 patients were reviewed. Hiatal BTM reinforcement, recurrence, and postoperative proton pump inhibitor use were reported by type of operation. Recurrence was higher in gastric bypass patients who underwent hiatal hernia repair with suture cruroplasty alone vs. those who also underwent hiatal BTM reinforcement (7.1% vs. 3.7%, P = .52) and significantly higher in gastric sleeve patients who underwent hiatal hernia repair with suture cruroplasty alone vs. those who also underwent hiatal BTM reinforcement (7.1% vs. .5%, P = .01). No patient required reoperation for hiatal hernia recurrence. DISCUSSION: Performing Roux-en-Y gastric bypass or vertical sleeve gastrectomy with concomitant hiatal hernia repair is safe and durable. Employing crural reinforcement with BTM may be of benefit in reducing recurrence rates of hiatal hernia, particularly in sleeve gastrectomy patients.

Phosphorylation, compartmentalization, and cardiac function.

Protein phosphorylation is a fundamental element of cell signaling. First discovered as a biochemical switch in glycogen metabolism, we now know that this posttranslational modification permeates all aspects of cellular behavior. In humans, over 540 protein kinases attach phosphate to acceptor amino acids, whereas around 160 phosphoprotein phosphatases remove phosphate to terminate signaling. Aberrant phosphorylation underlies disease, and kinase inhibitor drugs are increasingly used clinically as targeted therapies. Specificity in protein phosphorylation is achieved in part because kinases and phosphatases are spatially organized inside cells. A prototypic example is compartmentalization of the cyclic adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase A through association with A-kinase anchoring proteins. This configuration creates autonomous signaling islands where the anchored kinase is constrained in proximity to activators, effectors, and selected substates. This article primarily focuses on A kinase anchoring protein (AKAP) signaling in the heart with an emphasis on anchoring proteins that spatiotemporally coordinate excitation-contraction coupling and hypertrophic responses.

Mislocalization of protein kinase A drives pathology in Cushing's syndrome.

Mutations in the catalytic subunit of protein kinase A (PKAc) drive the stress hormone disorder adrenal Cushing's syndrome. We define mechanisms of action for the PKAc-L205R and W196R variants. Proximity proteomic techniques demonstrate that both Cushing's mutants are excluded from A kinase-anchoring protein (AKAP)-signaling islands, whereas live-cell photoactivation microscopy reveals that these kinase mutants indiscriminately diffuse throughout the cell. Only cAMP analog drugs that displace native PKAc from AKAPs enhance cortisol release. Rescue experiments that incorporate PKAc mutants into AKAP complexes abolish cortisol overproduction, indicating that kinase anchoring restores normal endocrine function. Analyses of adrenal-specific PKAc-W196R knockin mice and Cushing's syndrome patient tissue reveal defective signaling mechanisms of the disease. Surprisingly each Cushing's mutant engages a different mitogenic-signaling pathway, with upregulation of YAP/TAZ by PKAc-L205R and ERK kinase activation by PKAc-W196R. Thus, aberrant spatiotemporal regulation of each Cushing's variant promotes the transmission of distinct downstream pathogenic signals.

Biochemical Analysis of AKAP-Anchored PKA Signaling Complexes.

Generation of the prototypic second messenger cAMP instigates numerous signaling events. A major intracellular target of cAMP is Protein kinase A (PKA), a Ser/Thr protein kinase. Where and when this enzyme is activated inside the cell has profound implications on the functional impact of PKA. It is now well established that PKA signaling is focused locally into subcellular signaling "islands" or "signalosomes." The A-Kinase Anchoring Proteins (AKAPs) play a critical role in this process by dictating spatial and temporal aspects of PKA action. Genetically encoded biosensors, small molecule and peptide-based disruptors of PKA signaling are valuable tools for rigorous investigation of local PKA action at the biochemical level. This chapter focuses on approaches to evaluate PKA signaling islands, including a simple assay for monitoring the interaction of an AKAP with a tunable PKA holoenzyme. The latter approach evaluates the composition of PKA holoenzymes, in which regulatory subunits and catalytic subunits can be visualized in the presence of test compounds and small-molecule inhibitors.