Abstract
Mammalian cells express three Class II nonmuscle myosins (NM): NM2A, NM2B, and NM2C. The three NM2s have well established essential roles in cell motility, adhesion, and cytokinesis and less well defined roles in vesicle transport and other processes that would require association of NM2s with cell membranes. Previous evidence for the mechanism of NM2-membrane association includes direct interaction of NM2s with membrane lipids and indirect interaction by association of NM2s with membrane-bound F-actin or peripheral membrane proteins. Direct binding of NM2s to phosphatidylserine-liposomes, but not to phosphatidylcholine-liposomes, has been reported, but the molecular basis of the interaction between NM2s and acidic phospholipids has not been previously investigated. We now show that filamentous, full-length NM2A, NM2B, and NM2C and monomeric, non-filamentous heavy meromyosin bind to liposomes containing one or more acidic phospholipids (phosphatidylserine, phosphatidylinositol 4,5-diphosphate, and phosphatidylinositol 3,4,5-triphosphate) but do not bind to 100% phosphatidylcholine-liposomes. Binding of NM2s to acidic liposomes occurs predominantly through interaction of the liposomes with the regulatory light chain (RLC) binding site in the myosin heavy chain with concomitant dissociation of the RLC. Phosphorylation of myosin-bound RLC by myosin light chain kinase substantially inhibits binding to liposomes of both filamentous NM2 and non-filamentous heavy meromyosin; the addition of excess unbound RLC, but not excess unbound essential light chain, competes with liposome binding. Consistent with the in vitro data, we show that endogenous and expressed NM2A associates with the plasma membrane of HeLa cells and fibrosarcoma cells independently of F-actin.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.