GO:0031489 myosin V binding: Mechanism, Genes and Research

Myosin V binding (GO:0031489) is a molecular function that describes the binding of a protein or other molecule to a class V myosin. Class V myosins are dimeric motor proteins that move along actin filaments and are central to intracellular transport, including the delivery of secretory vesicles, organelles, and RNA-protein complexes to specific cellular locations. The term captures the physical interaction between a binding partner and the myosin V motor, which is often the first step in recruiting cargo or regulatory factors to the motor. Because myosin V binding underlies the spatial organization of the cytoplasm, it is a key node in studies of cell polarity, membrane trafficking, and organelle inheritance. Researchers study myosin V binding to understand how cells position their contents, how motor activity is switched on and off, and how defects in these interactions contribute to disease. For example, the myosin V motor Myo2 in budding yeast is activated by binding secretory cargo and released in coordination with Rab/exocyst function, illustrating that binding is not merely a static interaction but a regulated event that controls motor activity. In humans, mutations in myosin V genes and their binding partners are associated with disorders of the liver, pigmentation, and nervous system. The kinetic properties of myosin V, including its weak binding states, have been characterized to explain how binding partners influence motor stepping. This article provides a research-grade overview of GO:0031489, covering its definition, the biological processes it supports, the structural components involved, the molecular mechanism, key genes, regulation, disease links, and experimental methods including CRISPR-based models. All statements are grounded in the verified literature cited by number.

GO:0031489 (myosin V binding) is a molecular function term defined as binding to a class V myosin. Myosin V is a dimeric molecule involved in intracellular transport. In practice, this means any protein, lipid, or nucleic acid that physically interacts with a myosin V motor, typically through its tail or globular domain, is annotated with this term. The binding event can serve to recruit cargo, regulate motor activity, or localize the motor to specific cellular compartments.

Myosin V binding is important because it controls the spatial and temporal delivery of cellular components, a process essential for cell polarity, secretion, and organelle inheritance. Disruption of these interactions leads to defects in intracellular transport that underlie human diseases such as Progressive Familial Intrahepatic Cholestasis, where mutations in myosin V binding partners impair bile canalicular transport. Understanding myosin V binding also informs the design of experimental models to study motor-driven trafficking and to identify therapeutic targets.

The following genes and proteins are central to myosin V binding and its associated transport processes.

Myosin V binding is regulated at multiple levels. Cargo binding itself activates the motor and coordinates its release with Rab/exocyst function, ensuring that transport is coupled to vesicle fusion. Small GTPases such as Rab11 and Rab27a recruit specific adaptors that link cargo to myosin V, providing spatial and temporal control. The light chain-binding domain of myosin V binds calmodulin and other light chains, which modulate motor activity in response to calcium signals. Additionally, the mechanochemical cycle includes weak binding states that are sensitive to load and nucleotide state, allowing fine-tuning of processive movement. In yeast, the adaptor Ldm1 and its receptor Ldo16 mediate actin-dependent lipid droplet motility, illustrating cargo-specific regulation.

Mutations in MYO5B, a class V myosin, and its binding partners cause Progressive Familial Intrahepatic Cholestasis, a group of inherited disorders characterized by impaired bile secretion. Myosin V binding is critical for the apical recycling of bile canalicular proteins, and disruption of these interactions leads to cholestasis. Research models using patient-derived cells and CRISPR-edited organoids are helping to dissect the specific contributions of myosin V binding defects.

MYO5A mutations that impair myosin V binding to melanosomes cause Griscelli syndrome, characterized by hypopigmentation and immunodeficiency. The motor's ability to bind cargo adaptors such as melanophilin is essential for melanosome transport, and loss of this binding leads to perinuclear accumulation of melanosomes. This provides a clear example of how myosin V binding defects manifest in human disease.

Myosin V binding is also important in neurons, where it transports vesicles and RNA-protein complexes. Disruption of these interactions has been linked to developmental delays and neurological symptoms in some patients with MYO5A mutations. The precise mechanisms are still under investigation, but the role of myosin V in intracellular transport suggests that binding defects could contribute to synaptic dysfunction.

Fluorescent tagging of myosin V and its cargo allows real-time visualization of binding and movement. For example, GFP-tagged Myo2 in yeast has been used to track secretory vesicles and lipid droplets. This method reveals the dynamics of myosin V binding and processive movement.

Purified myosin V and cargo adaptors can be used in actin gliding assays or single-molecule binding assays to measure motor activity and binding affinity. Kinetic characterization of weak binding states has been performed using stopped-flow and fluorescence methods. These assays provide quantitative parameters for myosin V binding.

Affinity purification coupled with mass spectrometry can identify novel myosin V binding partners. This approach has been used to map the interactome of class V myosins and their adaptors. Such studies reveal context-dependent binding networks.

Genome-wide CRISPR knockout screens can identify genes required for myosin V binding and transport. For example, screens in yeast or mammalian cells can uncover adaptors and regulators. These screens are powerful for discovering new components of the transport machinery.

Researchers studying myosin V binding-related genes often need to determine whether a candidate gene is causally involved in transport, disease, or both. EDITGENE provides a comprehensive suite of CRISPR services to create precisely engineered cell models for such investigations.

GO:0031489 myosin V binding is a fundamental molecular function that governs the interaction between cargo and the class V myosin motor, enabling precise intracellular transport. Its importance spans basic cell biology, development, and human disease, with mutations in myosin V genes and their adaptors leading to conditions such as Progressive Familial Intrahepatic Cholestasis and Griscelli syndrome. Continued research using advanced imaging, proteomics, and CRISPR-based models will further illuminate how these interactions are regulated and how they can be targeted therapeutically.