Non-muscle myosin-IIA is critical for podocyte f-actin organization, contractility, and attenuation of cell motility

Development of Clinically Viable Non-Muscle Myosin II Small Molecule Inhibitors with Broad Therapeutic Potential

Non-muscle myosin II (NMII), a molecular motor that regulates critical processes such as cytokinesis and neuronal synaptic plasticity, has substantial therapeutic potential. However, translating this potential to in vivo use has been hampered by the lack of selective tools. The most prototypical non-selective inhibitor, blebbistatin inactivates both NMII and cardiac myosin II (CMII), a key regulator of heart function. Using rational drug design, we developed a series of NMII inhibitors that improve tolerability by selectively targeting NMII over CMII, including MT-228, which has excellent properties such as high brain penetration and efficacy in preclinical models of stimulant use disorder, which has no current FDA-approved therapies. The structure of MT-228 bound to myosin II provides insight into its 17-fold selectivity for NMII over CMII. MT-228's broad therapeutic window opens the door to new disease treatments and provides valuable tools for the scientific community, along with promising leads for future medication development.

Highlights

Research suggests numerous indications, from axon regeneration and cancer, would benefit from a small molecule inhibitor of non-muscle myosin II, a molecular motor that regulates the actin cytoskeleton. Current chemical probe options are very limited and lack sufficient safety for in vivo studies, which we show is primarily due to potent inhibition of cardiac myosin II.Rational design that focused on improving target selectivity over the pan-myosin II inhibitor, blebbistatin, led to the identification of MT-228, a small molecule inhibitor with a wide therapeutic window.High-resolution structure of MT-228 bound to myosin II reveals that selectivity results from a different positioning compared to blebbistatin and an important sequence difference between cardiac and non-muscle myosin II in the inhibitor binding pocket.A single administration of MT-228 shows long-lasting efficacy in animal models of stimulant use disorder, a current unmet and rapidly escalating need with no FDA-approved treatments.

Non-Muscle Myosin II A: Friend or Foe in Cancer?

Non-muscle myosin IIA (NM IIA) is a motor protein that belongs to the myosin II family. The myosin heavy chain 9 (MYH9) gene encodes the heavy chain of NM IIA. NM IIA is a hexamer and contains three pairs of peptides, which include the dimer of heavy chains, essential light chains, and regulatory light chains. NM IIA is a part of the actomyosin complex that generates mechanical force and tension to carry out essential cellular functions, including adhesion, cytokinesis, migration, and the maintenance of cell shape and polarity. These functions are regulated via light and heavy chain phosphorylation at different amino acid residues. Apart from physiological functions, NM IIA is also linked to the development of cancer and genetic and neurological disorders. MYH9 gene mutations result in the development of several autosomal dominant disorders, such as May-Hegglin anomaly (MHA) and Epstein syndrome (EPS). Multiple studies have reported NM IIA as a tumor suppressor in melanoma and head and neck squamous cell carcinoma; however, studies also indicate that NM IIA is a critical player in promoting tumorigenesis, chemoradiotherapy resistance, and stemness. The ROCK-NM IIA pathway regulates cellular movement and shape via the control of cytoskeletal dynamics. In addition, the ROCK-NM IIA pathway is dysregulated in various solid tumors and leukemia. Currently, there are very few compounds targeting NM IIA, and most of these compounds are still being studied in preclinical models. This review provides comprehensive evidence highlighting the dual role of NM IIA in multiple cancer types and summarizes the signaling networks involved in tumorigenesis. Furthermore, we also discuss the role of NM IIA as a potential therapeutic target with a focus on the ROCK-NM IIA pathway.

MYH9-related inherited thrombocytopenia: the genetic spectrum, underlying mechanisms, clinical phenotypes, diagnosis, and management approaches

Inherited thrombocytopenias have been considered exceedingly rare for a long time, but recent advances have facilitated diagnosis and greatly enabled the discovery of new causative genes. MYH9-related disease (MYH9-RD) represents one of the most frequent forms of inherited thrombocytopenia, usually presenting with nonspecific clinical manifestations, which renders it difficult to establish an accurate diagnosis. MYH9-RD is an autosomal dominant-inherited thrombocytopenia caused by deleterious variants in the MYH9 gene encoding the heavy chain of nonmuscle myosin IIA. Patients with MYH9-RD usually present with thrombocytopenia and platelet macrocytosis at birth or in infancy, and most of them may develop one or more extrahematologic manifestations of progressive nephritis, sensorial hearing loss, presenile cataracts, and elevated liver enzymatic levels during childhood and adult life. Here, we have reviewed recent advances in the study of MYH9-RD, which aims to provide an updated and comprehensive summary of the current knowledge and improve our understanding of the genetic spectrum, underlying mechanisms, clinical phenotypes, diagnosis, and management approaches of this rare disease. Importantly, our goal is to enable physicians to better understand this rare disease and highlight the critical role of genetic etiologic analysis in ensuring accurate diagnosis, clinical management, and genetic counseling while avoiding ineffective and potentially harmful therapies for MYH9-RD patients.

Loss of Calponin 2 causes age-progressive proteinuria in mice

Proteinuria is a major manifestation of kidney disease, reflecting injuries of glomerular podocytes. Actin cytoskeleton plays a pivotal role in stabilizing the foot processes of podocytes against the hydrostatic pressure of filtration. Calponin is an actin associated protein that regulates mechanical tension-related cytoskeleton functions and its role in podocytes has not been established. Here we studied the kidney phenotypes of calponin isoform 2 knockout (KO) mice. Urine samples were examined to quantify the ratio of albumin and creatinine. Kidney tissue samples were collected for histology and ultrastructural studies. A mouse podocyte cell line (E11) was used to study the expression and cellular localization of calponin 2. In comparison with wild-type (WT) controls, calponin 2 KO mice showed age-progressive high proteinuria and degeneration of renal glomeruli. High levels of calponin 2 are expressed in E11 podocytes and colocalized with actin stress fibers, tropomyosin and myosin IIA. Electron microscopy showed that aging calponin 2 KO mice had effacement of the podocyte foot processes and increased thickness of the glomerular basement membrane as compared to that of WT control. The findings demonstrate that deletion of calponin 2 aggravates age-progressive degeneration of the glomerular structure and function as filtration barrier. The critical role of calponin 2 in podocytes suggests a molecular target for understanding the pathogenesis of proteinuria and therapeutic development.

Nidogen1-enriched extracellular vesicles accelerate angiogenesis and bone regeneration by targeting Myosin-10 to regulate endothelial cell adhesion

The technique bottleneck of repairing large bone defects with tissue engineered bone is the vascularization of tissue engineered grafts. Although some studies have shown that extracellular vesicles (EVs) derived from bone marrow mesenchymal stem cells (BMSCs) promote bone healing and repair by accelerating angiogenesis, the effector molecules and the mechanism remain unclear, which fail to provide ideas for the future research and development of cell-free interventions. Here, we found that Nidogen1-enriched EV (EV-NID1) derived from BMSCs interferes with the formation and assembly of focal adhesions (FAs) by targeting myosin-10, thereby reducing the adhesion strength of rat arterial endothelial cells (RAECs) to the extracellular matrix (ECM), and enhancing the migration and angiogenesis potential of RAECs. Moreover, by delivery with composite hydrogel, EV-NID1 is demonstrated to promote angiogenesis and bone regeneration in rat femoral defects. This study identifies the intracellular binding target of EV-NID1 and further elucidates a novel approach and mechanism, thereby providing a cell-free construction strategy with precise targets for the development of vascularized tissue engineering products.

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Nidogen1 is enriched in extracellular vesicles (EV-NID1) derived from BMSCs.

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EV-NID1 interferes with the formation and assembly of focal adhesions (FAs).

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Myosin-10 was identified as the intracellular binding target of EV-NID1.

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The composite hydrogel loaded with EV-NID1 promotes the repair of bone defects by accelerating angiogenesis.

Association of the myosin heavy chain 9 gene single nucleotide polymorphism with inflammatory bowel disease

Background

To date, the cause of inflammatory bowel disease (IBD) remains a mystery. A balance between cell proliferation and apoptosis maintains intestinal tissue homeostasis. Dissociation-induced myosin-actin contraction results in stem cell apoptosis. This study aiming to evaluate the influence of the myosin heavy chain 9 (MYH9) gene single nucleotide polymorphisms (SNPs) on inflammatory bowel disease.

Subjects

and methods: The study carried on eighty patients with IBD and seventy controls. All participants subjected to history taking, thorough physical examination, colonoscopy and laboratory investigations. Genotyping performed for rs4821480 and rs3752462 by SNP assay real-time PCR methods.

Results

On analyzing rs3752462 CT and TT genotypes were significantly more frequent in IBD patients as compared to controls with 4.6 fold increase in the risk of IBD. While on analyzing rs4821480, The TG and GG genotypes have significant increased distribution among the IBD patients as compared to the controls with 5.3 fold increase in the risk of IBD and higher prevalence of GG genotype in patients with low hemoglobin level and higher BMI.

Conclusion

The rs3752462 T allele and rs4821480 G allele of MYH9 are associated with more susceptibility to IBD.

The Amot/integrin protein complex transmits mechanical forces required for vascular expansion

Vascular development is a complex multistep process involving the coordination of cellular functions such as migration, proliferation, and differentiation. How mechanical forces generated by cells and transmission of these physical forces control vascular development is poorly understood. Using an endothelial-specific genetic model in mice, we show that deletion of the scaffold protein Angiomotin (Amot) inhibits migration and expansion of the physiological and pathological vascular network. We further show that Amot is required for tip cell migration and the extension of cellular filopodia. Exploiting in vivo and in vitro molecular approaches, we show that Amot binds Talin and is essential for relaying forces between fibronectin and the cytoskeleton. Finally, we provide evidence that Amot is an important component of the endothelial integrin adhesome and propose that Amot integrates spatial cues from the extracellular matrix to form a functional vascular network.

Urine-Derived Epithelial Cells as Models for Genetic Kidney Diseases

Epithelial cells exfoliated in human urine can include cells anywhere from the urinary tract and kidneys; however, podocytes and proximal tubular epithelial cells (PTECs) are by far the most relevant cell types for the study of genetic kidney diseases. When maintained in vitro, they have been proven extremely valuable for discovering disease mechanisms and for the development of new therapies. Furthermore, cultured patient cells can individually represent their human sources and their specific variants for personalized medicine studies, which are recently gaining much interest. In this review, we summarize the methodology for establishing human podocyte and PTEC cell lines from urine and highlight their importance as kidney disease cell models. We explore the well-established and recent techniques of cell isolation, quantification, immortalization and characterization, and we describe their current and future applications.

MYH9 suppresses melanoma tumorigenesis, metastasis and regulates tumor microenvironment

Non-muscle myosin IIA heavy chain (MYH9) has been implicated in many physiological and pathological functions including cell adhesion, polarity, motility to cancer. However, its role in melanoma remains unexplored. The aim of our study was to evaluate the role of MYH9 in melanoma tumor development and metastasis and further to find out the potential underlying mechanisms. In this study, we evaluated the in vitro migratory and invasive properties and in vivo tumor development and metastasis in C57BL/6 mice by silencing MYH9 in B16F10 melanoma cells. Knocking down MYH9 enhanced migration and invasiveness of B16F10 cells in vitro. Furthermore, MYH9 silencing accelerated tumor growth and metastasis in melanoma subcutaneous and intravenous mouse models. Next, oncogenes analysis revealed epithelial-mesenchymal transition and Erk signaling pathway are being regulated with MYH9 expression. Finally, MYH9 silencing in B16F10 cells modulates the tumor microenvironment by manipulating the leukocytes and macrophages infiltration in tumors. These findings established the opposing role of MYH9 as a tumor suppressor in melanoma suggesting specific MYH9 based approaches in therapeutics.

Effect of donor non-muscle myosin heavy chain (MYH9) gene polymorphisms on clinically relevant kidney allograft dysfunction

BACKGROUND

Despite its established association with chronic kidney disease (CKD) the role of myosin-9 (MYH9) gene variation on transplanted kidney function remains unknown. This study aimed at evaluating the effect of donor MYH9 nephrogenic variants on renal allograft function within the first post transplantation year.

METHODS

In the longitudinal kidney transplant study 207 deceased donors were genotyped for previously known risk MYH9 single nucleotide polymorphisms (SNPs). The predictor was MYH9 high-risk variants status. The primary outcome was mean eGFR found in low vs. high risk MYH9 genotypes between third and twelfth post-transplant month, the secondary outcome was the risk of proteinuria.

RESULTS

Distribution of genotypes remained in Hardy-Weinberg equilibrium. The T allele of rs3752462 (dominant model, TT or TC vs. CC) was associated with higher filtration rate (P = 0.05) in a multivariate analysis after adjusting for delayed graft function and donor sex. Two G alleles of rs136211 (recessive model, GG vs. GA or AA) resulted in doubling the risk of proteinuria (OR = 2.22; 95% CI = 1.18-4.37, P = 0.017) after adjusting for donor and recipient sex.

CONCLUSION

Deceased donor kidneys of European descent harboring MYH9 SNPs rs3752462 T allele show significantly superior estimated filtration rate while those of rs136211 GG genotype excessive risk of proteinuria. These findings, if replicated, may further inform and improve individualization of allocation and treatment policies.

NudCL2 regulates cell migration by stabilizing both myosin-9 and LIS1 with Hsp90

Cell migration plays pivotal roles in many biological processes; however, its underlying mechanism remains unclear. Here, we find that NudC-like protein 2 (NudCL2), a cochaperone of heat shock protein 90 (Hsp90), modulates cell migration by stabilizing both myosin-9 and lissencephaly protein 1 (LIS1). Either knockdown or knockout of NudCL2 significantly increases single-cell migration, but has no significant effect on collective cell migration. Immunoprecipitation–mass spectrometry and western blotting analyses reveal that NudCL2 binds to myosin-9 in mammalian cells. Depletion of NudCL2 not only decreases myosin-9 protein levels, but also results in actin disorganization. Ectopic expression of myosin-9 efficiently reverses defects in actin disorganization and single-cell migration in cells depleted of NudCL2. Interestingly, knockdown of myosin-9 increases both single and collective cell migration. Depletion of LIS1, a NudCL2 client protein, suppresses both single and collective cell migration, which exhibits the opposite effect compared with myosin-9 depletion. Co-depletion of myosin-9 and LIS1 promotes single-cell migration, resembling the phenotype caused by NudCL2 depletion. Furthermore, inhibition of Hsp90 ATPase activity also reduces the Hsp90-interacting protein myosin-9 stability and increases single-cell migration. Forced expression of Hsp90 efficiently reverses myosin-9 protein instability and the defects induced by NudCL2 depletion, but not vice versa. Taken together, these data suggest that NudCL2 plays an important role in the precise regulation of cell migration by stabilizing both myosin-9 and LIS1 via Hsp90 pathway.

Actomyosin-dependent invasion of endothelial sprouts in collagen

During sprouting angiogenesis-the growth of blood vessels from the existing vasculature-endothelial cells (ECs) adopt an elongated invasive form and exert forces at cell-cell and cell-matrix interaction sites. These cell shape changes and cellular tractions require extensive reorganizations of the actomyosin network. However, the respective roles of actin and myosin for endothelial sprouting are not fully elucidated. In this study, we further investigate these roles by treating 2D-migrating and 3D-sprouting ECs with chemical compounds targeting either myosin or actin. These treatments affected the endothelial cytoskeleton drastically and reduced the invasive response in a compound-specific manner; pointing toward a tight control of the actin and myosin activity during sprouting. Clusters in the data further illustrate that endothelial sprout morphology is sensitive to the in vitro model mechanical microenvironment and directs future research toward mechanical substrate guidance as a strategy for promoting engineered tissue vascularization. In summary, our results add to a growing corpus of research highlighting a key role of the cytoskeleton for sprouting angiogenesis.

FNDC3B 3'-UTR shortening escapes from microRNA-mediated gene repression and promotes nasopharyngeal carcinoma progression

Alternative polyadenylation (APA), which induces shortening of the 3'-UTR, is emerging as an important feature in cancer development and progression. Nevertheless, the effects and mechanisms of APA-induced 3'-UTR shortening in nasopharyngeal carcinoma (NPC) remain largely unclear. Fibronectin type III domain containing 3B (FNDC3B) tended to use proximal polyadenylation site and produce shorter 3'-UTR according to our previous sequencing study. Herein, we found that FNDC3B with shorter 3'-UTR could escape from miRNA-mediated gene repression, and caused its increased expression in NPC. Knocking down of FNDC3B inhibited NPC cell proliferation, migration, invasion, and metastasis in vitro and in vivo. Overexpression of FNDC3B, especially those with shorter 3'-UTR, promoted NPC progression. Furthermore, the mechanism study revealed that FNDC3B could bind to and stabilize myosin heavy chain 9 (MYH9) to activate the Wnt/β-catenin signaling pathway. In addition, MYH9 could reverse the inhibitory effects of FNDC3B knockdown in NPC. Altogether, our results suggested that the 3'-UTR shortening of FNDC3B mRNA mediated its overexpression in NPC and promoted NPC progression by targeting MYH9. This newly identified FNDC3B-MYH9-Wnt/β-catenin axis could represent potential targets for individualized treatment in NPC.

MYH9-related disease: it does exist, may be more frequent than you think and requires specific therapy

In this issue of ckj, Tabibzadeh et al. report one of the largest series of patients with MYH9 mutations and kidney disease. The cardinal manifestation of MYH9-related disease is thrombocytopenia with giant platelets. The population frequency of pathogenic MYH9 mutations may be at least 1 in 20 000. The literature abounds in misdiagnosed cases treated for idiopathic thrombocytopenic purpura with immune suppressants and even splenectomy. Additional manifestations include neurosensorial deafness and proteinuric and hematuric progressive kidney disease (at some point, it was called Alport syndrome with macrothrombocytopenia), leucocyte inclusions, cataracts and liver enzyme abnormalities, resulting in different names for different manifestation combinations (MATINS, May-Hegglin anomaly, Fechtner, Epstein and Sebastian syndromes, and deafness AD 17). The penetrance and severity of kidney disease are very variable, which may obscure the autosomal dominant inheritance. A correct diagnosis will both preclude unnecessary and potentially dangerous therapeutic interventions and allow genetic counselling and adequate treatment. Morphological erythrocyte, granulocyte and platelet abnormalities may allow the future development of high-throughput screening techniques adapted to clinical peripheral blood flow cytometers.

MYH9 Promotes Growth and Metastasis via Activation of MAPK/AKT Signaling in Colorectal Cancer

The contractile protein MYH9 (non-muscle myosin IIA) is an actin-binding protein that plays a fundamental role in cell adhesion, migration, and division. However, its distinct role in colorectal cancer (CRC) still remains unidentified. In this study, we detected significant MYH9 overexpression in CRC samples compared with paired normal tissues using western blotting and tissue microarray immunohistochemistry (IHC). Moreover, analysis of patient clinical information demonstrated that MYH9 overexpression was strongly correlated with lymph node metastasis and poor overall survival. Endogenous overexpression of MYH9 enhanced the ability of cell proliferation and migration in vitro, and accelerated CRC growth in mouse models. Silencing of MYH9 revealed repressive effects on CRC cells in vitro and in vivo. Furthermore, primary biomechanics that involved MAPK/AKT signaling mediated epithelial-mesenchymal transition (EMT) was uncovered underlying MYH9 dependent cell behaviors. Collectively, our data showed that MYH9 significantly promoted tumorigenesis by regulating MAPK/AKT signaling, and was remarkably correlated with poor prognosis in CRC. MYH9 may thus be a novel biomarker and drug target in the diagnosis and treatment of CRC.

IL-6 increases podocyte motility via MLC-mediated focal adhesion impairment and cytoskeleton disassembly

The disturbance of podocyte motility is an essential pathogenic mechanisms of foot process effacement during proteinuric diseases, and myosin light chain (MLC) is a pivotal component in regulating the motility of podocytes. Inflammatory cytokine interleukin-6 (IL-6) has been reported to induce podocyte abnormalities by various mechanisms, however, whether aberrant cell motility contributes to the IL-6-induced podocyte injury remains unknown. Here, by wound healing, transwell, and cell migration assays, we confirmed that IL-6 accelerates the motility of podocyte. Simultaneously, the phosphorylation of MLC is elevated along with perturbed focal adhesion (FAs) and cytoskeleton. Next, via genetic and pharmacologic interruption of MLC or its phosphorylation we revealed that the activation of MLC is implicated in IL-6-mediated podocyte hypermotility as well as the disassembly of FAs and F-actin. By using stattic, an inhibitor for STAT3 phosphorylation, we uncovered that STAT3 activation is the upstream event for MLC phosphorylation and the following aberrant motility of podocytes. Additionally, we found that calcitriol markedly attenuates podocyte hypermotility via blocking STAT3-MLC. In conclusion, our study demonstrated that IL-6 interrupts FAs dynamic, cytoskeleton organization, and eventually leads to podocyte hypermotility via STAT3/MLC, whereas calcitriol exerts its protective role by inhibiting this pathway. These findings enrich the mechanisms accounting for IL-6-mediated podocyte injury from the standpoint of cell motility and provide a novel therapeutic target for podocyte disorders.

Clinic, pathogenic mechanisms and drug testing of two inherited thrombocytopenias, ANKRD26-related Thrombocytopenia and MYH9-related diseases

Inherited thrombocytopenias (ITs) are a heterogeneous group of disorders characterized by low platelet count resulting in impaired hemostasis. Patients can have spontaneous hemorrhages and/or excessive bleedings provoked by hemostatic challenges as trauma or surgery. To date, ITs encompass 32 different rare monogenic disorders caused by mutations of 30 genes. This review will focus on the major discoveries that have been made in the last years on the diagnosis, treatment and molecular mechanisms of ANKRD26-Related Thrombocytopenia and MYH9-Related Diseases. Furthermore, we will discuss the use a Thrombopoietin mimetic as a novel approach to treat the thrombocytopenia in these patients. We will propose the use of a new 3D bone marrow model to study the mechanisms of action of these drugs and to test their efficacy and safety in patients. The overall purpose of this review is to point out that important progresses have been made in understanding the pathogenesis of ANKRD26-Related Thrombocytopenia and MYH9-Related Diseases and new therapeutic approaches have been proposed and tested. Future advancement in this research will rely in the development of more physiological models to study the regulation of human platelet biogenesis, disease mechanisms and specific pharmacologic targets.

Mechanical challenges and cytoskeletal impairments in focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a histologically defined form of kidney injury typically mediated by podocyte dysfunction. Podocytes rely on their intricate actin-based cytoskeleton to maintain the glomerular filtration barrier in the face of mechanical challenges resulting from pulsatile blood flow and filtration of this blood flow. This review summarizes the mechanical challenges faced by podocytes in the form of stretch and shear stress, both of which may play a role in the progression of podocyte dysfunction and detachment. It also reviews how podocytes respond to these mechanical challenges in dynamic fashion through rearranging their cytoskeleton, triggering various biochemical pathways, and, in some disease states, altering their morphology in the form of foot process effacement. Furthermore, this review highlights the growing body of evidence identifying several mutations of important cytoskeleton proteins as causes of FSGS. Lastly, it synthesizes the above evidence to show that a better understanding of how these mutations leave podocytes vulnerable to the mechanical challenges they face is essential to better understanding the mechanisms by which they lead to disease. The review concludes with future research directions to fill this gap and some novel techniques with which to pursue these directions.

Regulation of Mitochondrial Structure and Dynamics by the Cytoskeleton and Mechanical Factors

Mitochondria supply cells with energy in the form of ATP, guide apoptosis, and contribute to calcium buffering and reactive oxygen species production. To support these diverse functions, mitochondria form an extensive network with smaller clusters that are able to move along microtubules aided by motor proteins. Mitochondria are also associated with the actin network, which is involved in cellular responses to various mechanical factors. In this review, we discuss mitochondrial structure and function in relation to the cytoskeleton and various mechanical factors influencing cell functions. We first summarize the morphological features of mitochondria with an emphasis on fission and fusion as well as how network properties govern function. We then review the relationship between the mitochondria and the cytoskeletal structures, including mechanical interactions. We also discuss how stretch and its dynamic pattern affect mitochondrial structure and function. Finally, we present preliminary data on how extracellular matrix stiffness influences mitochondrial morphology and ATP generation. We conclude by discussing the more general role that mitochondria may play in mechanobiology and how the mechanosensitivity of mitochondria may contribute to the development of several diseases and aging.