MYL6 Human

What is the basic structure of human MYL6 protein?

Human MYL6 is a 151 amino acid protein that functions as a regulatory light chain of myosin . As part of the myosin complex, it serves as one of the nonphosphorylatable alkali light chains in the hexameric ATPase cellular motor protein structure . The protein's primary sequence contains specific domains that facilitate its interaction with myosin heavy chains and other binding partners. Unlike some other myosin light chains, MYL6 does not bind calcium, which distinguishes its regulatory properties . The full-length recombinant human MYL6 protein is available commercially with high purity (>90%) for research purposes, typically expressed in systems like Escherichia coli for experimental applications .

How does MYL6 differ from other myosin light chains?

MYL6 belongs to the nonphosphorylatable alkali light chain category of myosin light chains, unlike the phosphorylatable regulatory light chains such as MYL12A and MYL12B . This fundamental difference affects how MYL6 contributes to myosin function and regulation. While regulatory light chains like MYL9 undergo phosphorylation to control myosin activity, MYL6 serves a more structural role in the myosin complex . Additionally, MYL6 is expressed in both smooth muscle and non-muscle tissues, giving it a broader tissue distribution pattern compared to some more tissue-specific myosin light chains . Its inability to bind calcium also contrasts with calcium-binding properties of certain other myosin light chains, suggesting different mechanisms of action in cellular contractility regulation .

What are the known transcript variants and isoforms of MYL6?

The human MYL6 gene produces at least two transcript variants encoding different isoforms that have been identified . These variants result from alternative splicing events and potentially serve tissue-specific or context-dependent functions. Several pseudogenes representing genomic sequences related to MYL6 have also been described in the human genome . The diverse nomenclature found in literature (including MLC-3, MLC1SM, MLC3NM, MLC3SM, ESMLC, LC17, etc.) reflects this complexity and historical identification of different forms across various tissue types and experimental systems . Researchers should be careful to specify which isoform they are working with in experimental descriptions, as functional differences may exist between variants.

What is the tissue distribution pattern of MYL6 expression?

MYL6 exhibits a broad tissue distribution pattern, being expressed in both smooth muscle and non-muscle tissues . Unlike some myosin light chains with highly restricted expression profiles, MYL6's widespread presence suggests fundamental roles in cellular function across multiple tissue types. Expression analysis through various databases indicates particularly notable expression in muscle-containing tissues, though specific expression levels vary across tissue types. When conducting tissue-specific research, investigators should consider these differential expression patterns and how they might influence experimental design and interpretation. Quantitative comparison of MYL6 expression across tissues would require normalized expression analysis, which could be accomplished through qPCR, western blotting with appropriate loading controls, or analysis of publicly available RNA-seq datasets.

What are the key protein interaction partners of MYL6?

Protein interaction analysis reveals that MYL6 has strong predicted functional partnerships with several proteins, particularly those involved in cytoskeletal organization and cell motility . The primary interaction partners include:

Most significantly, recent research has identified a novel interaction between MYL6 and kindlin-3 in platelets, revealing a previously unknown role in integrin αIIbβ3 activation . This interaction demonstrates that beyond its structural role in the myosin complex, MYL6 participates in signaling pathways crucial for cellular adhesion and aggregation functions .

How does MYL6 contribute to cytoskeletal dynamics?

As a component of the myosin complex, MYL6 plays a fundamental role in cytoskeletal dynamics by contributing to the structural and functional properties of myosin motor proteins . Myosin motor proteins generate force for cellular contractility, organelle movement, and cell shape changes. MYL6 specifically functions as a nonphosphorylatable alkali light chain within this complex, helping to stabilize the myosin heavy chain structure and modulate its interaction with actin filaments . This contributes to proper cytoskeletal architecture and contractile force generation. The protein's involvement in the cytoskeleton is evidenced by its classification among proteins of the cytoskeleton in biological databases . Researchers investigating cytoskeletal dynamics should consider MYL6's contributions, particularly in non-muscle cells where its function may be less characterized compared to traditional muscle cells.

What is the role of MYL6 in platelet function and hemostasis?

Recent research has revealed a critical and previously unrecognized role for MYL6 in platelet function and hemostasis . MYL6 has been identified as a novel binding partner for kindlin-3 in platelets, where it supports integrin αIIbβ3 activation . Studies using Myl6-deficient mouse models (Myl6 fl/flPF4-Cre) demonstrated that:

• MYL6 deficiency leads to significant macrothrombocytopenia resulting from defective proplatelet formation

• Integrin αIIbβ3 activation is significantly suppressed in the absence of MYL6

• Platelet aggregation is substantially impaired without MYL6

• MYL6 contributes to the avidity modulation of integrin αIIbβ3 by binding to kindlin-3

• Blood coagulation ability is impaired in Myl6-deficient mice

These findings establish MYL6 as an essential component in both hemostatic and thrombotic functions, linking cytoskeletal dynamics to integrin signaling in platelets . The mechanism appears to involve MYL6-mediated crosstalk between integrin αIIbβ3 and myosin in platelets, providing a molecular bridge that had not been previously characterized .

What are the recommended methods for studying MYL6 protein interactions?

For investigating MYL6 protein interactions, researchers should consider multiple complementary approaches:

• Co-immunoprecipitation (Co-IP): This technique can identify native protein complexes containing MYL6. Using specific antibodies against MYL6 or its suspected binding partners (such as kindlin-3 or myosin heavy chains), researchers can pull down protein complexes from cell lysates and analyze them by western blotting .

• Proximity Ligation Assays (PLA): For detecting protein-protein interactions in situ with high sensitivity, PLA can visualize the spatial proximity of MYL6 and its interaction partners within cells, providing information about the cellular context of these interactions.

• Yeast Two-Hybrid (Y2H) Screening: While having limitations for cytoskeletal proteins, Y2H can be used as an initial screen to identify potential novel binding partners of MYL6, which can then be confirmed by other methods.

• Recombinant Protein Binding Assays: Using purified recombinant MYL6 protein (available commercially with >90% purity) , direct binding studies with potential partners can establish binding affinities and domains involved in interaction.

• Bioinformatic Analysis: Tools like STRING database can predict functional partnerships based on multiple lines of evidence, as shown for MYL6's predicted interactions with MYH9, MYL12B, MYH10, and MYL12A .

When investigating novel interactions, such as the MYL6-kindlin-3 interaction, a combination of these approaches provides the most robust evidence for physiologically relevant protein associations.

What genetic models are available for studying MYL6 function?

Several genetic approaches are available for studying MYL6 function in different experimental systems:

• Conditional Knockout Mouse Models: The Myl6 fl/flPF4-Cre mouse model with MYL6 deficiency specifically in the megakaryocyte lineage has been developed and characterized . This model exhibits macrothrombocytopenia, defective proplatelet formation, impaired integrin αIIbβ3 activation, and defects in both hemostatic and thrombotic functions .

• siRNA/shRNA Knockdown: For in vitro studies, transient or stable knockdown of MYL6 expression can be achieved using RNA interference approaches in relevant cell types, including smooth muscle cells, fibroblasts, or platelet precursor cell lines.

• CRISPR/Cas9 Gene Editing: CRISPR-based approaches allow for precise modification of the MYL6 gene, including complete knockout, introduction of point mutations, or tagging with fluorescent proteins for localization studies.

• Domain-Specific Mutants: Expression of MYL6 variants with specific mutations or truncations can help identify functional domains important for binding to kindlin-3, myosin heavy chains, or other partners.

When selecting a model system, researchers should consider the tissue-specific context of their research question, as MYL6 functions may vary between different cell types and physiological processes.

What is known about MYL6's role in disease states?

MYL6 has been associated with several disease conditions, though the mechanisms require further investigation:

• Adrenal Gland Pheochromocytoma: MYL6 has been associated with this rare tumor of the adrenal glands . The molecular mechanism linking MYL6 to tumor development is not fully characterized but may involve altered cytoskeletal dynamics affecting cell proliferation or migration.

• Noonan Syndrome 2: This genetic disorder characterized by abnormal development of multiple parts of the body has been linked to MYL6 . The specific contribution of MYL6 to the pathogenesis of this syndrome requires further elucidation.

• Thrombotic Disorders: Recent research demonstrating MYL6's role in platelet function suggests it may be implicated in thrombotic diseases . Deficiency of MYL6 in platelets leads to impaired blood coagulation and defects in both hemostatic and thrombotic functions in mouse models .

• Cardiovascular Disorders: Given its expression in smooth muscle and role in cytoskeletal dynamics, alterations in MYL6 function could potentially contribute to cardiovascular pathologies, though this remains to be fully explored.

Researchers investigating disease mechanisms should consider MYL6's functional roles in cytoskeletal organization, platelet function, and potential contributions to cellular signaling pathways when examining these and other pathological conditions.

How might MYL6 be targeted therapeutically?

Based on current understanding of MYL6 function, several potential therapeutic approaches could be considered:

• Modulation of Platelet Function: Given MYL6's role in integrin αIIbβ3 activation and platelet aggregation, therapeutic modulation could potentially address thrombotic disorders . Targeting the MYL6-kindlin-3 interaction might provide a novel approach to anti-platelet therapy with potentially different side effect profiles compared to current therapies.

• Cytoskeletal-Targeting Approaches: As a component of the myosin complex involved in cytoskeletal dynamics, modulation of MYL6 function could potentially affect cell motility, shape, and mechanical properties. This might be relevant in contexts such as cancer metastasis or fibrotic conditions.

• Diagnostic Biomarker Development: Rather than direct targeting, MYL6 expression or modifications might serve as biomarkers for certain disease states, particularly those involving alterations in platelet function or cytoskeletal dysregulation.

When considering therapeutic approaches, researchers must account for MYL6's broad tissue distribution and fundamental cellular functions , which may limit the specificity of direct targeting strategies and increase potential side effects. Context-specific targeting approaches, such as platelet-targeted delivery systems, might help overcome these limitations.

How do post-translational modifications regulate MYL6 function?

While MYL6 is classified as a nonphosphorylatable alkali light chain, other potential post-translational modifications (PTMs) may regulate its function in specific contexts. Advanced research in this area should explore:

• PTM Profiling: Comprehensive mass spectrometry analysis to identify and quantify all PTMs on MYL6 across different tissues and cellular conditions. This could reveal context-specific modifications beyond phosphorylation, such as acetylation, methylation, ubiquitination, or SUMOylation.

• Functional Impact Assessment: For identified PTMs, determine their functional consequences through site-directed mutagenesis (changing modified residues to non-modifiable amino acids) and analyzing effects on MYL6's binding to partners like kindlin-3 or myosin heavy chains.

• Regulatory Enzymes Identification: Identify the writers, erasers, and readers of MYL6 PTMs to understand the regulatory machinery controlling its modification state in response to cellular signals.

• Temporal Dynamics Analysis: Investigate how MYL6 modifications change during cellular processes like platelet activation, using time-course experiments with specific PTM antibodies or quantitative proteomics.

This research direction could reveal novel regulatory mechanisms for MYL6 function that extend beyond its structural role in the myosin complex.

What is the evolutionary significance of MYL6 conservation across species?

MYL6 is highly conserved across species, suggesting fundamental evolutionary importance. Advanced research in this area should address:

• Comparative Genomics Analysis: Detailed sequence comparison of MYL6 orthologs across diverse species to identify absolutely conserved regions likely critical for function versus more variable regions that might confer species-specific properties.

• Functional Conservation Testing: Experimental testing of whether MYL6 orthologs from different species can functionally substitute for one another in cellular contexts like platelet activation or cytoskeletal organization.

• Evolutionary Rate Analysis: Study of the evolutionary rate of MYL6 compared to other myosin light chains to understand selective pressures and functional constraints.

• Ancestral Sequence Reconstruction: Computational reconstruction of ancestral MYL6 sequences to understand the evolutionary trajectory of this protein and potentially identify key adaptive changes.

Understanding the evolutionary constraints on MYL6 structure and function could provide insights into its most fundamental roles in cellular physiology that have been maintained through evolutionary history.