Regulation of Myosin V-Cargo Interactions by Phosphorylation

82 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2004.Myosin V is required for the proper transport and localization of specific organelles along actin filaments in many cell types. Two independent kinases, Calcium/calmodulin-dependent kinase II (CaMKII) and p21-activated kinase-1 (PAK1), are able to phosphorylate the globular tail of myosin V. Mutation analysis and mass spectrometry were used to determine the actual site of phosphorylation for each kinase. The target of CaMKII phosphorylation is the serine residue at position 1650 in the globular tail of mouse myosin Va, while PAK1 phosphorylates the serine residue located at position 1649. The tandem localization of these two, independent phosphorylation sites suggests that this region of the protein is central to motor regulation. During mitosis, CaMKII phosphorylation of myosin V inhibits the ability of the motor to bind to Xenopus melanosomes. Similarly, myosin V recruitment to mouse phagosomes during phagocytosis is blocked by PAK1 phosphorylation. Thus, the binding of myosin V to cargo is regulated by phosphorylation of the tail domain, and may represent a common mechanism of regulation of vertebrate myosin V.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD