Linking Ras to myosin function: RasGEF Q, a Dictyostelium exchange factor for RasB, affects myosin II functions

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Paul A. Steimle, Assistant Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: Ras guanine nucleotide exchange factor (GEF) Q, a nucleotide exchange factor from Dictyostelium discoideum , is a 143-kD protein containing RasGEF domains and a DEP domain. We show that RasGEF Q can bind to F-actin, has the potential to form complexes with myosin heavy chain kinase (MHCK) A that contain active RasB, and is the predominant exchange factor for RasB. Overexpression of the RasGEF Q GEF domain activates RasB, causes enhanced recruitment of MHCK A to the cortex, and leads to cytokinesis defects in suspension, phenocopying cells expressing constitutively active RasB, and myosin-null mutants. RasGEF Q- mutants have defects in cell sorting and slug migration during later stages of development, in addition to cell polarity defects. Furthermore, RasGEF Q- mutants have increased levels of unphosphorylated myosin II, resulting in myosin II overassembly. Collectively, our results suggest that starvation signals through RasGEF Q to activate RasB, which then regulates processes requiring myosin II.

Additional Information

Publication
Journal of Cell Biology 181.5, 747-760
Language: English
Date: 2008
Keywords
Ras guanine nucleotide exchange factor, Dictyostelium discoideum, RasGEF Q, RasB, myosin II functions