Abstract
Myosin IXa (Myo9a) is a motor protein that is highly expressed in the brain. However, the role of Myo9a in neurons remains unknown. Here, we investigated Myo9a function in hippocampal synapses. In rat hippocampal neurons, Myo9a localizes to the postsynaptic density (PSD) and binds the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) GluA2 subunit. Myo9a+/- mice displayed a thicker PSD and increased levels of PSD95 and surface AMPAR expression. Furthermore, synaptic transmission, long-term potentiation (LTP) and cognitive functions were impaired in Myo9a+/- mice. Together, these results support a key role for Myo9a in controlling the molecular structure and function of hippocampal synapses.
Highlights
Myosin IXa (Myo9a, previously called myr7) is an actin-dependent motor protein of the unconventional myosin IX class
Our study is based on the finding that Myo9a and amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) are associated in the same molecular complex in hippocampal neurons
AMPARs are enriched at the postsynaptic density (PSD) of dendritic spines where they mediate most of the fast excitatory transmission (Bredt and Nicoll, 2003)
Summary
Myosin IXa (Myo9a, previously called myr7) is an actin-dependent motor protein of the unconventional myosin IX class. Myo9a is expressed in several tissues and is enriched in the brain and testes (Chieregatti et al, 1998; Gorman et al, 1999). Myo9a is detectable in all regions, in the hippocampus, cortex, and cerebellum, during both development and in adulthood (Chieregatti et al, 1998). Class IX myosins share a common structure: an N-terminal extension preceding a myosin head, a head (motor) domain, a neck with IQ motifs that bind light chains and a C-terminal tail containing a Rho-GTPase activating protein (RhoGAP) domain. The RhoGAP domain enables class IX myosins to inactivate small GTPases of the Rho family (Reinhard et al, 1995). The role of Myo9a in neurons has not yet been investigated
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