Myosin-Va-interacting protein, RILPL2, controls cell shape and neuronal morphogenesis via Rac signaling.
ABSTRACT Neuronal morphology plays an essential role in neuronal function. The establishment and maintenance of neuronal morphology is intimately linked to the actin cytoskeleton; however, the molecular mechanisms that regulate changes in neuronal morphology are poorly understood. Here we identify a novel myosin-Va (MyoVa)-interacting protein, RILPL2, which regulates cellular morphology. Overexpression of this protein in young or mature hippocampal neurons results in an increase in the number of spine-like protrusions. By contrast, knockdown of endogenous RILPL2 in neurons by short hairpin RNA (shRNA) interference results in reduced spine-like protrusions, a phenotype rescued by overexpression of an shRNA-insensitive RILPL2 mutant, suggesting a role for RILPL2 in both the establishment and maintenance of dendritic spines. Interestingly, we demonstrate that RILPL2 and the Rho GTPase Rac1 form a complex, and that RILPL2 is able to induce activation of Rac1 and its target, p21-activated kinase (Pak). Notably, both RILPL2-mediated morphological changes and activation of Rac1-Pak signaling were blocked by expression of a truncated tail form of MyoVa or MyoVa shRNA, demonstrating that MyoVa is crucial for proper RILPL2 function. This might represent a novel mechanism linking RILPL2, the motor protein MyoVa and Rac1 with neuronal structure and function.
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ABSTRACT: Myosin V (MyoV) motors have been implicated in the intracellular transport of diverse cargoes including vesicles, organelles, RNA-protein complexes and regulatory proteins. Here, we have solved the cargo-binding domain (CBD) structures of the three human MyoV paralogs (Va, Vb and Vc), revealing subtle structural changes that drive functional differentiation and a novel redox mechanism controlling the CBD dimerization process, which is unique for the MyoVc subclass. Moreover, the cargo- and motor-binding sites were structurally assigned indicating the conservation of residues involved in the recognition of adaptors for peroxisome transport and providing high-resolution insights into motor domain (MD) inhibition by CBD. These results contribute to understanding the structural requirements for cargo transport, auto-inhibition and regulatory mechanisms in myosin V motors.Journal of Biological Chemistry 10/2013; · 4.65 Impact Factor
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ABSTRACT: Myosins are a large family of actin-based cytoskeletal motors that use energy derived from ATP hydrolysis to generate movement and force. Myosins of classes II, V and VI have specific pre- and postsynaptic roles that are required for synapse function. They also facilitate several forms of synaptic plasticity. Interestingly, the myosins of these classes differ markedly in important aspects of their molecular mechanisms of function. Accordingly, their major roles at synapses are diverse and include the regulation of actin cytoskeleton dynamics in dendritic spines and powering of synaptic cargo transport.Nature Reviews Neuroscience 03/2013; · 26.48 Impact Factor
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ABSTRACT: Class V myosins (MyoV), the most studied unconventional myosins, recognize numerous cargos mainly via the motor's globular tail domain (GTD). Little is known regarding how MyoV-GTD recognizes such a diverse array of cargos specifically. Here, we solved the crystal structures of MyoVa-GTD in its apo-form and in complex with two distinct cargos, melanophilin and Rab interacting lysosomal protein-like 2. The apo-MyoVa-GTD structure indicates that most mutations found in patients with Griscelli syndrome, microvillus inclusion disease, or cancers or in "dilute" rodents likely impair the folding of GTD. The MyoVa-GTD/cargo complex structure reveals two distinct cargo-binding surfaces, one primarily via charge-charge interaction and the other mainly via hydrophobic interactions. Structural and biochemical analysis reveal the specific cargo-binding specificities of various isoforms of mammalian MyoV as well as very different cargo recognition mechanisms of MyoV between yeast and higher eukaryotes. The MyoVa-GTD structures resolved here provide a framework for future functional studies of vertebrate class V myosins.Proceedings of the National Academy of Sciences 06/2013; · 9.74 Impact Factor