Agonist-induced PIP2 Hydrolysis Inhibits Cortical Actin Dynamics: Regulation at a Global but not at a Micrometer Scale

Jacco van Rheenen, Kees Jalink, Thomas D. Pollard
2002 Molecular Biology of the Cell  
Phosphatidylinositol 4, 5-bisphosphate (PIP 2 ) at the inner leaflet of the plasma membrane has been proposed to locally regulate the actin cytoskeleton. Indeed, recent studies that use GFP-tagged pleckstrin homology domains (GFP-PH) as fluorescent PIP 2 sensors suggest that this lipid is enriched in membrane microdomains. Here we report that this concept needs revision. Using three distinct fluorescent GFP-tagged pleckstrin homology domains, we show that highly mobile GFP-PH patches colocalize
more » ... perfectly with various lipophilic membrane dyes and, hence, represent increased lipid content rather than PIP 2 -enriched microdomains. We show that bright patches are caused by submicroscopical folds and ruffles in the membrane that can be directly visualized at ϳ15 nm axial resolution with a novel numerically enhanced imaging method. F-actin motility is inhibited significantly by agonist-induced PIP 2 breakdown, and it resumes as soon as PIP 2 levels are back to normal. Thus, our data support a role for PIP 2 in the regulation of cortical actin, but they challenge a model in which spatial differences in PIP 2 regulation of the cytoskeleton exist at a micrometer scale. Article published online ahead of print. Mol. Biol. Cell 10.1091/ mbc.E02-04 -0231. Article and publication date are at www.molbiolcell.org/cgi/
doi:10.1091/mbc.e02-04-0231 pmid:12221130 pmcid:PMC124157 fatcat:gkuynrm6a5e5plmmizdptyg6x4