Abstract
Myosin V motors mediate cargo transport; however, the identity of neuronal molecules transported by these proteins remains unknown. Here we show that myosin Vb is expressed in several neuronal populations and associates with the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate-type glutamate receptor subunit GluR1. In developing hippocampal neurons, expression of the tail domain of myosin Vb, but not myosin Va, enhanced GluR1 accumulation in the soma and reduced its surface expression. These changes were accompanied by reduced GluR1 clustering and diminished frequency of excitatory but not inhibitory synaptic currents. Similar effects were observed upon expression of full-length myosin Vb lacking a C-terminal region required for binding to the small GTPase Rab11. In contrast, mutant myosin Vb did not change the localization of several other neurotransmitter receptors, including the glutamate receptor subunit NR1. These results reveal a novel mechanism for the transport of a specific glutamate receptor subunit in neurons mediated by a member of the myosin V family.
Highlights
Three known members of the myosin V family have been detected in brain extracts
To determine whether myosin Vb is expressed in neurons, we raised specific antibodies against the coiled-coil domain of myosin Vb, the region least conserved among members of the myosin V family [2]
In this study we have investigated the involvement of myosin V family members in the trafficking of a subset of neuronal proteins
Summary
Three known members of the myosin V family have been detected in brain extracts. The most studied member, myosin Va, is widely expressed in the brain [5]. Expression of truncated forms of various members of the myosin V family lacking the N-terminal motor domain but containing the globular tail domain leads to a dominant-negative phenotype in different cultured cell systems [11, 13,14,15,16,17] This dominant negative approach revealed an important role of myosin Va in the control of melanosome transport in melanocytes [18]. The association of myosin Vc with Rab8-positive endosomes is involved in transferrin trafficking in HeLa cells [11] These observations indicate that coupling of individual members of the myosin V family to a particular subset of endosomal proteins may control the specificity of cargo transported by these motors.
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