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; 288(47). DOI:10.1074/jbc.M113.507202 · 4.60 Impact Factor
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