Regulatory effects of the p38 mitogen-activated protein kinase-myosin light chain kinase pathway on the intestinal epithelial mechanical barrier and the mechanism of modified Pulsatilla decoction in the treatment of ulcerative colitis.

OBJECTIVE: To investigate the mechanism of the protective effect of modified Pulsatilla decoction (, MPD) on the mechanical barrier of the ulcerative colitis (UC) intestinal epithelium in vitro and in vivo. METHODS: We established an intestinal epithelial crypt cell line-6 cell barrier injury model by using lipopolysaccharide (LPS). The model was then treated with p38 mitogen-activated protein kinase-myosin light chain kinase (p38MAPK-MLCK) pathway inhibitors, p38MAPK-MLCK pathway silencing genes (si-p38MAPK, si-NF-κB, and si-MLCK), and MPD respectively. Transepithelial electronic resistance (TEER) measurements and permeability assays were performed to assess barrier function. Immunofluorescence staining of tight junctions (TJ) was performed. In in vivo experiment, dextran sodium sulfate-induced colitis rat model was conducted to evaluate the effect of MPD and mesalazine on UC. The rats were scored using the disease activity index based on their clinical symptoms. Transmission electron microscopy and hematoxylin-eosin staining were used to examine morphological changes in UC rats. Western blotting and real-time quantitative polymerase chain reaction were performed to examine the gene and protein expression of significant differential molecules. RESULTS: In in vitro study, LPS-induced intestinal barrier dysfunction was inhibited by p38MAPK-MLCK pathway inhibitors and p38MAPK-MLCK pathway gene silencing. Silencing of p38MAPK-MLCK pathway genes decreased TJ expression. MPD treatment partly restored the LPS-induced decreased in TEER and increase in permeability. MPD increased the gene and protein expression of TJ, while down-regulated the LPS-induced high expression of p-p38MAPK and p-MLC. In UC model rats, MPD could ameliorate body weight loss and disease activity index, relieve colonic pathology, up-regulate TJ expression as well as decrease the expression of p-p38MAPK and p-MLC in UC rat colonic mucosal tissue. CONCLUSIONS: The p38MAPK-MLCK signaling pathway can affect mechanical barrier function and TJ expression in the intestinal epithelium. MPD restores TJ expression and attenuates intestinal epithelial barrier damage by suppressing the p38MAPK-MLCK pathway.

Loss of myosin light chain kinase induces the cellular senescence associated secretory phenotype to promote breast epithelial cell migration.

Overexpression or activation of oncogenes or loss of tumor-suppressor genes can induce cellular senescence as a defense mechanism against tumor development, thereby maintaining cellular homeostasis. However, cancer cells can circumvent this senescent state and continue to spread. Myosin light chain kinase (MLCK) is downregulated in many breast cancers. Here we report that downregulation of MLCK in normal breast epithelial cells induces a senescence-associated secretory phenotype and stimulates migration. The reduction of MLCK results in increased p21Cip1 expression, dependent on p53 and the AKT-mammalian target of rapamycin pathway. Subsequently, p21Cip1 promotes the secretion of soluble ICAM-1, IL-1α, IL-6 and IL-8, thereby enhancing collective cell migration in a non-cell-autonomous manner. These findings provide new mechanistic insights into the role of MLCK in cellular senescence and cancer progression.

Activation of the ROCK/MYLK Pathway Affects Complex Molecular and Morphological Changes of the Trabecular Meshwork Associated With Ocular Hypertension.

Purpose: The Rho-associated protein kinase and myosin light chain kinase (ROCK/MYLK) pathway undeniably plays a pivotal role in the pathophysiology of primary open-angle glaucoma (POAG). In our study, we utilized both ocular hypertension (OHT) rabbit models and clinical investigations to gain invaluable insights that propel the development of novel treatments targeting proteins and genes associated with the trabecular meshwork (TM), thereby offering promising avenues for the management of POAG. Methods: Following microbead injections into the anterior chamber of the ocular cavity of rabbits, we observed elevated histiocyte numbers and immune scores for MYLK-4/ pMLC-2, alongside a reduction in the void space within the TM. Notably, treatment was performed with 0.1% ITRI-E-(S)-4046, a compound with dual kinase inhibitor (highly specific inhibitor of ROCK1/2 and MYLK4), significantly reduced intraocular pressure (IOP; P < 0.05) and expanded the void space within the TM (P < 0.0001) compared with OHT rabbits. In clinical investigations, we utilized whole transcriptome sequencing to analyze gene expression specifically related to the TM, obtained from patients (5 early-onset and 5 late-onset) undergoing trabeculectomy. Results: Our findings revealed 103 differential expression genes (DEGs) out of 265 molecules associated with the Rho family GTPase pathway, exhibiting a P value of 1.25E-10 and a z-score of -2.524. These results underscore significant differences between the early-onset and late-onset POAG and highlight the involvement of the ROCK/MYLK pathway. Conclusions: These findings underscore the critical involvement of the ROCK/MYLK pathway in both OHT-related and different onsets of POAG, providing valuable insights into the TM-related molecular mechanisms underlying the disease.

Cavß3 Contributes to the Maintenance of the Blood-Brain Barrier and Alleviates Symptoms of Experimental Autoimmune Encephalomyelitis.

BACKGROUND: Tight control of cytoplasmic Ca2+ concentration in endothelial cells is essential for the regulation of endothelial barrier function. Here, we investigated the role of Cavß3, a subunit of voltage-gated Ca2+ (Cav) channels, in modulating Ca2+ signaling in brain microvascular endothelial cells (BMECs) and how this contributes to the integrity of the blood-brain barrier. METHODS: We investigated the function of Cavß3 in BMECs by Ca2+ imaging and Western blot, examined the endothelial barrier function in vitro and the integrity of the blood-brain barrier in vivo, and evaluated disease course after induction of experimental autoimmune encephalomyelitis in mice using Cavß3-/- (Cavß3-deficient) mice as controls. RESULTS: We identified Cavß3 protein in BMECs, but electrophysiological recordings did not reveal significant Cav channel activity. In vivo, blood-brain barrier integrity was reduced in the absence of Cavß3. After induction of experimental autoimmune encephalomyelitis, Cavß3-/- mice showed earlier disease onset with exacerbated clinical disability and increased T-cell infiltration. In vitro, the transendothelial resistance of Cavß3-/- BMEC monolayers was lower than that of wild-type BMEC monolayers, and the organization of the junctional protein ZO-1 (zona occludens-1) was impaired. Thrombin stimulates inositol 1,4,5-trisphosphate-dependent Ca2+ release, which facilitates cell contraction and enhances endothelial barrier permeability via Ca2+-dependent phosphorylation of MLC (myosin light chain). These effects were more pronounced in Cavß3-/- than in wild-type BMECs, whereas the differences were abolished in the presence of the MLCK (MLC kinase) inhibitor ML-7. Expression of Cacnb3 cDNA in Cavß3-/- BMECs restored the wild-type phenotype. Coimmunoprecipitation and mass spectrometry demonstrated the association of Cavß3 with inositol 1,4,5-trisphosphate receptor proteins. CONCLUSIONS: Independent of its function as a subunit of Cav channels, Cavß3 interacts with the inositol 1,4,5-trisphosphate receptor and is involved in the tight control of cytoplasmic Ca2+ concentration and Ca2+-dependent MLC phosphorylation in BMECs, and this role of Cavß3 in BMECs contributes to blood-brain barrier integrity and attenuates the severity of experimental autoimmune encephalomyelitis disease.

The effects of high doses of selenium supplementation on mRNA and protein levels of cMLCK levels and total antioxidant capacity in rat heart tissue.

BACKGROUND: High doses of selenium are associated with heart disease prevalence in high-risk areas. Cardiac myosin light chain kinase (cMLCK) is an essential enzyme for normal function of heart tissue. Therefore, we studied the effect of high doses of selenium on the expression of cMLCK gene and its protein in normal heart tissue in rats. MATERIALS AND METHODS: Twenty male rats were randomly divided into four groups: control, Se 0.3mg/kg, Se 1.5mg/kg, and Se 3mg/kg. Sodium-selenite was administered orally into drinking water for 20 weeks. Se levels of heart tissue were measured by atomic absorption. Serum creatine phosphokinase (CPK) and total serum antioxidant capacity were measured. Moreover, the concentration of MLCK protein and the gene expression level of cMLCK in normal heart tissue were analyzed. RESULTS: Excess Se in dietary can significantly increase CPK. Se concentration of heart tissue in the Se 3mg/kg group was significantly higher than the control. cMLCK mRNA levels were decreased by 0.3mg/kg and 3mg/kg sodium selenite intake. There was no significant difference between the three groups for total antioxidant capacity and MLCK protein. CONCLUSION: High concentrations of selenium can probably effect on normal function of the heart tissue by changing the expression levels of cMLCK.

Aging aggravates aortic aneurysm and dissection via miR-1204-MYLK signaling axis in mice.

The mechanism by which aging induces aortic aneurysm and dissection (AAD) remains unclear. A total of 430 participants were recruited for the screening of differentially expressed plasma microRNAs (miRNAs). We found that miR-1204 is significantly increased in both the plasma and aorta of elder patients with AAD and is positively correlated with age. Cell senescence induces the expression of miR-1204 through p53 interaction with plasmacytoma variant translocation 1, and miR-1204 induces vascular smooth muscle cell (VSMC) senescence to form a positive feedback loop. Furthermore, miR-1204 aggravates angiotensin II-induced AAD formation, and inhibition of miR-1204 attenuates ß-aminopropionitrile monofumarate-induced AAD development in mice. Mechanistically, miR-1204 directly targets myosin light chain kinase (MYLK), leading to the acquisition of a senescence-associated secretory phenotype (SASP) by VSMCs and loss of their contractile phenotype. MYLK overexpression reverses miR-1204-induced VSMC senescence, SASP and contractile phenotypic changes, and the decrease of transforming growth factor-ß signaling pathway. Our findings suggest that aging aggravates AAD via the miR-1204-MYLK signaling axis.

Characterisation of the myosin light chain kinase (MLCK) gene of Locusta migratoria and the encoded MLCK.

Myosin light chain kinase (MLCK) is a dedicated kinase of myosin regulatory light chain (RLC), playing an essential role in the regulation of muscle contraction and cell motility. Much of the knowledge about MLCK comes from the study of vertebrate MLCK, and little is known about insect MLCK. Here, we identified the single MLCK gene in the locust Locusta migratoria, which spans over 1400 kb, includes 62 exons and accounts for at least five transcripts. We found that the five distinct transcripts of the locust MLCK gene are expressed in a tissue-specific manner, including three muscle-specific isoforms and two generic isoforms. To characterise the kinase activity of locust MLCK, we recombinantly expressed LmMLCK-G, the smallest locust MLCK isoform, in insect Sf9 cells. We demonstrated that LmMLCK-G is a Ca2+/calmodulin-dependent kinase that specifically phosphorylates serine 50 of locust muscle myosin RLC (LmRLC). Additionally, we found that almost all LmRLC molecules in the flight muscle and the hindleg muscles of adult locusts are phosphorylated.

Mechanisms underlying distinct subcellular localization and regulation of epithelial long myosin light-chain kinase splice variants.

Intestinal epithelia express two long myosin light-chain kinase (MLCK) splice variants, MLCK1 and MLCK2, which differ by the absence of a complete immunoglobulin (Ig)-like domain 3 within MLCK2. MLCK1 is preferentially associated with the perijunctional actomyosin ring at steady state, and this localization is enhanced by inflammatory stimuli including tumor necrosis factor (TNF). Here, we sought to identify MLCK1 domains that direct perijunctional MLCK1 localization and their relevance to disease. Ileal biopsies from Crohn's disease patients demonstrated preferential increases in MLCK1 expression and perijunctional localization relative to healthy controls. In contrast to MLCK1, MLCK2 expressed in intestinal epithelia is predominantly associated with basal stress fibers, and the two isoforms have distinct effects on epithelial migration and barrier regulation. MLCK1(Ig1-4) and MLCK1(Ig1-3), but not MLCK2(Ig1-4) or MLCK1(Ig3), directly bind to F-actin in vitro and direct perijunctional recruitment in intestinal epithelial cells. Further study showed that Ig1 is unnecessary, but that, like Ig3, the unstructured linker between Ig1 and Ig2 (Ig1/2us) is essential for recruitment. Despite being unable to bind F-actin or direct recruitment independently, Ig3 does have dominant negative functions that allow it to displace perijunctional MLCK1, increase steady-state barrier function, prevent TNF-induced MLCK1 recruitment, and attenuate TNF-induced barrier loss. These data define the minimal domain required for MLCK1 localization and provide mechanistic insight into the MLCK1 recruitment process. Overall, the results create a foundation for development of molecularly targeted therapies that target key domains to prevent MLCK1 recruitment, restore barrier function, and limit inflammatory bowel disease progression.

IGF2BP3-mediated enhanced stability of MYLK represses MSC adipogenesis and alleviates obesity and insulin resistance in HFD mice.

Mesenchymal stem cells (MSCs) hold immense potential as multipotent stem cells and serve as a primary source of adipocytes. The process of MSC adipogenesis plays a crucial role in maintaining systemic metabolic homeostasis and has garnered significant attention in tissue bioengineering. N6-methyladenosine (m6A), the most prevalent RNA modification, is known to regulate cell fate and disease. However, the precise involvement of m6A readers in MSC adipogenesis remains unclear. In this study, we investigated the impact of IGF2BP3, a prominent m6A reader, on MSC adipogenesis. Our findings revealed a decrease in IGF2BP3 expression during the natural adipogenic differentiation of MSCs. Furthermore, IGF2BP3 was found to repress MSC adipogenesis by augmenting the levels of MYLK, a calcium/calmodulin-dependent kinase. Mechanistically, IGF2BP3 interacted with MYLK mRNA in an m6A-dependent manner, extending its half-life and subsequently inhibiting the phosphorylation of the ERK1/2 pathway, thereby impeding the adipogenic differentiation of MSCs. Additionally, we successfully achieved the overexpression of IGF2BP3 through intraperitoneal injection of adeno-associated virus serotype Rec2, which specifically targeted adipose tissue. This intervention resulted in reduced body weight and improved insulin resistance in high-fat diet mice. Overall, our study provides novel insights into the role of IGF2BP3 in MSC adipogenesis, shedding light on adipocyte-related disorders and presenting potential targets for related biomedical applications.

The MYPT2-regulated striated muscle-specific myosin light chain phosphatase limits cardiac myosin phosphorylation in vivo.

The physiological importance of cardiac myosin regulatory light chain (RLC) phosphorylation by its dedicated cardiac myosin light chain kinase has been established in both humans and mice. Constitutive RLC-phosphorylation, regulated by the balanced activities of cardiac myosin light chain kinase and myosin light chain phosphatase (MLCP), is fundamental to the biochemical and physiological properties of myofilaments. However, limited information is available on cardiac MLCP. In this study, we hypothesized that the striated muscle-specific MLCP regulatory subunit, MYPT2, targets the phosphatase catalytic subunit to cardiac myosin, contributing to the maintenance of cardiac function in vivo through the regulation of RLC-phosphorylation. To test this hypothesis, we generated a floxed-PPP1R12B mouse model crossed with a cardiac-specific Mer-Cre-Mer to conditionally ablate MYPT2 in adult cardiomyocytes. Immunofluorescence microscopy using the gene-ablated tissue as a control confirmed the localization of MYPT2 to regions where it overlaps with a subset of RLC. Biochemical analysis revealed an increase in RLC-phosphorylation in vivo. The loss of MYPT2 demonstrated significant protection against pressure overload-induced hypertrophy, as evidenced by heart weight, qPCR of hypertrophy-associated genes, measurements of myocyte diameters, and expression of ß-MHC protein. Furthermore, mantATP chase assays revealed an increased ratio of myosin heads distributed to the interfilament space in MYPT2-ablated heart muscle fibers, confirming that RLC-phosphorylation regulated by MLCP, enhances cardiac performance in vivo. Our findings establish MYPT2 as the regulatory subunit of cardiac MLCP, distinct from the ubiquitously expressed canonical smooth muscle MLCP. Targeting MYPT2 to increase cardiac RLC-phosphorylation in vivo may improve baseline cardiac performance, thereby attenuating pathological hypertrophy.

Aortic dissection in a young male with persistent ductus arteriosus and a novel variant in MYLK.

Pathogenic variants in several genes involved in the function or regulation of smooth muscle cells (SMC) are known to predispose to congenital heart disease and thoracic aortic aneurysm and dissection (TAAD). Variants in MYLK are primarily known to predispose to TAAD, but a growing body of evidence points toward MYLK also playing an essential role in the regulation of SMC contraction outside the aorta. In this case report, we present a patient with co-occurrence of persistent ductus arteriosus (PDA) and thoracic aortic dissection. Genetic analyses revealed a novel splice acceptor variant (c.3986-1G > A) in MYLK, which segregated with disease in the family. RNA-analyses on fibroblasts showed that the variant induced skipping of exon 24, which resulted in an in-frame deletion of 101 amino acids. These findings suggest that MYLK-associated disease could include a broader phenotypic spectrum than isolated TAAD, including PDA and obstructive pulmonary disease. Genetic analyses could be considered in families with TAAD and PDA or obstructive pulmonary disease.

LncRNA MYLK antisense RNA 1 activates cell division cycle 42/Neutal Wiskott-Aldrich syndrome protein pathway via microRNA-101-5p to accelerate epithelial-to-mesenchymal transition of colon cancer cells.

Long noncoding RNA MYLK antisense RNA 1 (MYLK-AS1) is the crux in multiple diseases. Therefore, the purpose of this study was to investigate the possible mechanism of MYLK-AS1. A total of 62 colon cancer (CC) specimens and paired adjacent normal tissues were collected, and the expression of MYLK-AS1, microRNA (miR)-101-5p/cell division cycle 42 (CDC42) was detected. CC cell lines were transfected with MYLK-AS1, miR-101-5p, CDC42-related plasmids, and the biological functions and markers of epithelial-mesenchymal transition (EMT) were analyzed. The binding relationship between MYLK-AS1, miR-101-5p, and CDC42 was evaluated. In CC tissues and cell lines, MYLK-AS1 and CDC42 were highly expressed, and miR-101-5p was lowly expressed. Inhibition of MYLK-AS1 or upregulation of miR-101-5p can inhibit CC cell growth and EMT. miR-101-5p inhibited CDC42/N-wasp axis activation in CC cells by targeting CDC42. Knockdown of CDC42 or upregulation of miR-101-5p partially reversed the effects caused by upregulation of MYLK-AS1. MYLK-AS1, which is significantly upregulated in CC, may be a molecular sponge for miR-101-5p, and MYLK-AS1 promotes the activation of the CDC42/N-wasp axis in CC cells by targeting CDC42 through miR-101-5p, which in turn promotes tumor development. MYLK-AS1 may be a potential biomarker and target for CC therapy.

Striated preferentially expressed gene deficiency leads to mitochondrial dysfunction in developing cardiomyocytes.

A deficiency of striated preferentially expressed gene (Speg), a member of the myosin light chain kinase family, results in abnormal myofibril structure and function of immature cardiomyocytes (CMs), corresponding with a dilated cardiomyopathy, heart failure and perinatal death. Mitochondrial development plays a role in cardiomyocyte maturation. Therefore, this study investigated whether Speg deficiency ( - / - ) in CMs would result in mitochondrial abnormalities. Speg wild-type and Speg-/- C57BL/6 littermate mice were utilized for assessment of mitochondrial structure by transmission electron and confocal microscopies. Speg was expressed in the first and second heart fields at embryonic (E) day 7.5, prior to the expression of mitochondrial Na+/Ca2+/Li+ exchanger (NCLX) at E8.5. Decreases in NCLX expression (E11.5) and the mitochondrial-to-nuclear DNA ratio (E13.5) were observed in Speg-/- hearts. Imaging of E18.5 Speg-/- hearts revealed abnormal mitochondrial cristae, corresponding with decreased ATP production in cells fed glucose or palmitate, increased levels of mitochondrial superoxide and depolarization of mitochondrial membrane potential. Interestingly, phosphorylated (p) PGC-1α, a key mediator of mitochondrial development, was significantly reduced in Speg-/- hearts during screening for targeted genes. Besides Z-line expression, Speg partially co-localized with PGC-1α in the sarcomeric region and was found in the same complex by co-immunoprecipitation. Overexpression of a Speg internal serine/threonine kinase domain in Speg-/- CMs promoted translocation of pPGC-1α into the nucleus, and restored ATP production that was abolished by siRNA-mediated silencing of PGC-1α. Our results demonstrate a critical role of Speg in mitochondrial development and energy metabolism in CMs, mediated in part by phosphorylation of PGC-1α.

Hub biomarkers in ultrasound-guided bladder cancer and osteosarcoma: Myosin light chain kinase and caldesmon.

Bladder cancer and osteosarcoma are 2 types of cancers that originate from epithelial tissues inside the bladder and bone or muscle tissues. Ultrasound-guided biopsies provide crucial support for the diagnosis and treatment of bladder cancer and osteosarcoma. However, the relationship between myosin light chain kinase (MYLK) and caldesmon (CALD1) and bladder cancer and osteosarcoma remains unclear. The bladder cancer datasets GSE65635 and GSE100926, the osteosarcoma dataset GSE39058, were obtained from gene expression omnibus. Differentially expressed genes (DEGs) were screened and weighted gene co-expression network analysis was performed. The construction and analysis of protein-protein interaction network, functional enrichment analysis, gene set enrichment analysis. Gene expression heat map was drawn and immune infiltration analysis was performed. The comparative toxicogenomics database analysis were performed to find disease most related to core gene. Western blotting experiments were performed. TargetScan screened miRNAs that regulated central DEGs. We obtained 54 DEGs. Functional enrichment analysis revealed significant enrichment in terms of cellular differentiation, cartilage development, skeletal development, muscle actin cytoskeleton, actin filament, Rho GTPase binding, DNA binding, fibroblast binding, MAPK signaling pathway, apoptosis, and cancer pathways. Gene set enrichment analysis indicated that DEGs were primarily enriched in terms of skeletal development, cartilage development, muscle actin cytoskeleton, MAPK signaling pathway, and apoptosis. The immune infiltration analysis showed that when T cells regulatory were highly expressed, Eosinophils exhibited a similar high expression, suggesting a strong positive correlation between T cells regulatory and Eosinophils, which might influence the disease progression in osteosarcoma. We identified 6 core genes (SRF, CTSK, MYLK, VCAN, MEF2C, CALD1). MYLK and CALD1 were significantly correlated with survival rate and exhibited lower expression in bladder cancer and osteosarcoma samples compared to normal samples. Comparative toxicogenomics database analysis results indicated associations of core genes with osteosarcoma, bladder tumors, bladder diseases, tumors, inflammation, and necrosis. The results of Western blotting showed that the expression levels of MYLK and CALD1 in bladder cancer and osteosarcoma were lower than those in normal tissues. MYLK and CALD1 likely play a role in regulating muscle contraction and smooth muscle function in bladder cancer and osteosarcoma. The lower expression of MYLK and CALD1 is associated with poorer prognosis.

Molecular Insights into the MLCK Activation by CaM.

Calmodulin (CaM) is a universal regulatory protein that modulates numerous cellular processes by using calcium (Ca2+) as the signal. In smooth muscle cells (SMC), one major target of CaM is myosin light chain kinase (MLCK), a kinase that phosphorylates the myosin regulatory light chain and thereby regulates cell contraction. In the absence of CaM, MLCK remains inhibited by its autoinhibitory domain (AID). While it is well established that CaM activates MLCK, the molecular interactions between these two proteins remain elusive due to the lack of structural data. In this work, we constructed a molecular model of mammalian CaM (mCaM) in complex with MLCK leveraging AlphaFold, published biochemical data, and protein-protein docking. The model, along with a strategic set of CaM mutants including a inhibitory variant soybean CaM isoform 4 (sCaM-4), was subject to molecular dynamics (MD) simulations. Using principal component analysis (PCA), we mapped out the transition path for the removal of the AID from the MLCK kinase domain to provide molecular basis of MLCK activation. Additionally, we established MLCK conformations that correspond to the active and inactive states of the kinase. We showed that mCaM and sCaM-4 cause MLCK to undergo the transition to the active and inactive states, respectively. Using two structural metrics, we computed the probabilities of MLCK activation by different CaM variants, which were in good agreement with the experimental data. Distributions along these metrics revealed that different inhibitory CaM variants impair MLCK activation through unique mechanisms. We finally identified molecular contacts that contribute to the MLCK activation by CaM. Overall, we report a de novo molecular model of CaM-MLCK that provides insights into the molecular mechanism of MLCK activation by CaM. The mechanism requires effective removal of the AID while preserving an active configuration of the kinase domain. This mechanism may be shared by other MLCK isoforms and potentially other structurally similar kinases with CaM-mediated regulatory domains.

MYLK and CALD1 as molecular targets in bladder cancer.

Bladder cancer (BC) is a malignant tumor that occurs in bladder mucosa. However, relationship between myosin light chain kinase (MYLK) and CALD1 and BC remains unclear. The BC datasets GSE65635 and GSE100926 were downloaded from gene expression omnibus by GPL14951 and GPL14550. Multiple datasets were merged and batched. Differentially expressed genes (DEGs) were screened and weighted gene co-expression network analysis was performed. gene ontology (GO) and Kyoto Encyclopedia of Gene and Genome analysis, gene set enrichment analysis, immune infiltration analysis, survival analysis and Comparative Toxicogenomics Database were performed. TargetScan screened miRNAs that regulated central DEGs. 1026 DEGs were identified. According to GO analysis, DEGs were mainly enriched in cancer pathway, cGMP-PKG signaling pathway, Apelin signaling pathway and proteoglycans in cancer. The enrichment items are similar to GO and Kyoto Encyclopedia of Gene and Genome enrichment projects for DEGs, which were mainly enriched in cancer pathways and leukocyte trans-endothelial cell migration. Among enrichment projects of metascape, GO has regulation of the enzyme-linked receptor protein signaling pathway and silk-based process, as well as an enrichment network stained by enrichment terms and P values. Nine core genes (ACTA2, MYLK, MYH11, MYL9, ACTG2, TPM1, TPM2, TAGLN and CALD1) were obtained, which were highly expressed in tumor tissue samples and lowly expressed in normal tissue samples. Nine genes were associated with necrosis, inflammation, tumor, edema, and ureteral obstruction. MYLK and CALD1 are highly expressed in the BC. The higher expression of MYLK and CALD1, the worse prognosis.

Novel Long Noncoding RNAs, LINC01093 and MYLK-AS1, Serve as Potential Diagnostic and Prognostic Biomarkers or Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the most fatal human malignancies worldwide. In this research, we aimed to identify long noncoding RNAs (lncRNAs) as biomarkers for HCC diagnosis and prognosis. lncRNA expression profiles were obtained from Gene Expression Omnibus and The Cancer Genome Atlas databases. The differentially expressed lncRNAs between HCC and adjacent tissues were analyzed with bioinformatic tools. Four lncRNAs with area under the curve of the receiver operating characteristic curve >0.9 were selected from both datasets. Univariate and Kaplan-Meier analyses were performed to obtain LINC01093, MYLK-AS1, and MCM3AP-AS1 as the optimal diagnostic and prognostic biomarkers. Finally, qPCR confirmed that LINC01093 and MYLK-AS1 were significantly differentially expressed in HCC and adjacent normal tissues. In general, we demonstrated that novel lncRNAs, LINC01093 and MYLK-AS1, could be used as potential diagnostic and prognostic biomarkers for HCC.

Restoration of Cardiac Myosin Light Chain Kinase Ameliorates Systolic Dysfunction by Reducing Superrelaxed Myosin.

BACKGROUND: Cardiac-specific myosin light chain kinase (cMLCK), encoded by MYLK3, regulates cardiac contractility through phosphorylation of ventricular myosin regulatory light chain. However, the pathophysiological and therapeutic implications of cMLCK in human heart failure remain unclear. We aimed to investigate whether cMLCK dysregulation causes cardiac dysfunction and whether the restoration of cMLCK could be a novel myotropic therapy for systolic heart failure. METHODS: We generated the knock-in mice (Mylk3+/fs and Mylk3fs/fs) with a familial dilated cardiomyopathy-associated MYLK3 frameshift mutation (MYLK3+/fs) that had been identified previously by us (c.1951-1G>T; p.P639Vfs*15) and the human induced pluripotent stem cell-derived cardiomyocytes from the carrier of the mutation. We also developed a new small-molecule activator of cMLCK (LEUO-1154). RESULTS: Both mice (Mylk3+/fs and Mylk3fs/fs) showed reduced cMLCK expression due to nonsense-mediated messenger RNA decay, reduced MLC2v (ventricular myosin regulatory light chain) phosphorylation in the myocardium, and systolic dysfunction in a cMLCK dose-dependent manner. Consistent with this result, myocardium from the mutant mice showed an increased ratio of cardiac superrelaxation/disordered relaxation states that may contribute to impaired cardiac contractility. The phenotypes observed in the knock-in mice were rescued by cMLCK replenishment through the AAV9_MYLK3 vector. Human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation reduced cMLCK expression by 50% and contractile dysfunction, accompanied by an increased superrelaxation/disordered relaxation ratio. CRISPR-mediated gene correction, or cMLCK replenishment by AAV9_MYLK3 vector, successfully recovered cMLCK expression, the superrelaxation/disordered relaxation ratio, and contractile dysfunction. LEUO-1154 increased human cMLCK activity ≈2-fold in the Vmax for ventricular myosin regulatory light chain phosphorylation without affecting the Km. LEUO-1154 treatment of human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation restored the ventricular myosin regulatory light chain phosphorylation level and superrelaxation/disordered relaxation ratio and improved cardiac contractility without affecting calcium transients, indicating that the cMLCK activator acts as a myotrope. Finally, human myocardium from advanced heart failure with a wide variety of causes had a significantly lower MYLK3/PPP1R12B messenger RNA expression ratio than control hearts, suggesting an altered balance between myosin regulatory light chain kinase and phosphatase in the failing myocardium, irrespective of the causes. CONCLUSIONS: cMLCK dysregulation contributes to the development of cardiac systolic dysfunction in humans. Our strategy to restore cMLCK activity could form the basis of a novel myotropic therapy for advanced systolic heart failure.

Phosphatase regulatory subunit MYPT2 knockout partially compensates for the cardiac dysfunction in mice caused by lack of myosin light chain kinase 3.

Cardiac contraction is modulated by the phosphorylation state of myosin regulatory light chain 2 (MLC-2v). The level of MLC-2v phosphorylation is dependent on the opposing activities of MLC kinases and phosphatases. The predominant MLC phosphatase found in cardiac myocytes contains Myosin Phosphatase Targeting Subunit 2 (MYPT2). Overexpression of MYPT2 in cardiac myocytes results in a decreased level of MLC phosphorylation, reduced left ventricular contraction, and induction of hypertrophy; however, the effect of knocking out MYPT2 on cardiac function is unknown. We obtained heterozygous mice containing a MYPT2 null allele from the Mutant Mouse Resource Center. These mice were produced in a C57BL/6N background which lack MLCK3, the main regulatory light chain kinase in cardiac myocytes. We found that mice null for MYPT2 were viable and had no obvious phenotypic abnormality when compared to WT mice. Additionally, we determined that WT C57BL/6N mice had a low basal level of MLC-2v phosphorylation, which was significantly increased when MYPT2 was absent. At 12-weeks, MYPT2 KO mice had smaller hearts and showed downregulation of genes involved in cardiac remodeling. Using cardiac echo, we found that 24-week-old male MYPT2 KO mice had decreased heart size with increased fractional shortening compared to their MYPT2 WT littermates. Collectively, these studies highlight the important role that MYPT2 plays in cardiac function in vivo and demonstrate that its deletion can partially compensate for the lack of MLCK3.