Abstract
The neuronal spine is a small, actin-rich dendritic or somatic protrusion that serves as the postsynaptic compartment of the excitatory synapse. The morphology of the spine reflects the activity of the synapse and is regulated by the dynamics of the actin cytoskeleton inside, which is controlled by actin binding proteins such as non-muscle myosin. Previously, we demonstrated that the subcellular localization and function of myosin IIb are regulated by its binding partner, filamin-A interacting protein (FILIP). However, how the subcellular distribution of myosin IIb is controlled by FILIP is not yet known. The objective of this study was to identify potential binding partners of FILIP that contribute to its regulation of non-muscle myosin IIb. Pull-down assays detected a 70-kDa protein that was identified by mass spectrometry to be the chaperone protein Hsc70. The binding of Hsc70 to FILIP was controlled by the adenosine triphosphatase (ATPase) activity of Hsc70. Further, FILIP bound to Hsc70 via a domain that was not required for binding non-muscle myosin IIb. Inhibition of ATPase activity of Hsc70 impaired the effect of FILIP on the subcellular distribution of non-muscle myosin IIb. Further, in primary cultured neurons, an inhibitor of Hsc70 impeded the morphological change in spines induced by FILIP. Collectively, these results demonstrate that Hsc70 interacts with FILIP to mediate its effects on non-muscle myosin IIb and to regulate spine morphology.
Highlights
Many actin-binding proteins, such as myosins, control actin cytoskeleton dynamics
We recently reported that the expression of filamin-A interacting protein (FILIP, FILIP-1) results in the alteration of the subcellular distribution of non-muscle myosin IIb in cultured cells
Actin stress fibers consist of actin fibers and actin binding proteins, including non-muscle myosin, our results indicate that the reduction in actin stress fiber formation due to FILIP expression is independent of changes to the subcellular distribution of non-muscle myosin IIb
Summary
Many actin-binding proteins, such as myosins, control actin cytoskeleton dynamics. Myosins are divided into at least twenty-four classes and have roles in numerous cellular functions, including cytokinesis, organelle transport, cell polarization, and signal transduction [1,2]. Class II myosins form thick filaments and have a role in cellular contraction [2]. Muscle type myosin II assembles and forms thick filaments, which are PLOS ONE | DOI:10.1371/journal.pone.0172257. FILIP and Hsc control subcellular distribution of NMHCIIb. Foundation, Takeda Science Foundation and the NOVARTIS Foundation (Japan) for the Promotion of Science (to M.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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