RRC ID 41576
Author Yonemura S, Matsui T, Tsukita S, Tsukita S.
Title Rho-dependent and -independent activation mechanisms of ezrin/radixin/moesin proteins: an essential role for polyphosphoinositides in vivo.
Journal J Cell Sci
Abstract Ezrin/radixin/moesin (ERM) proteins crosslink actin filaments to plasma membranes and are involved in the organization of the cortical cytoskeleton, especially in the formation of microvilli. ERM proteins are reported to be activated as crosslinkers in a Rho-dependent manner and are stabilized when phosphorylated at their C-terminal threonine residue to create C-terminal threonine-phosphorylated ERM proteins (CPERMs). Using a CPERM-specific mAb, we have shown, in vivo, that treatment with C3 transferase (a Rho inactivator) or staurosporine (a protein kinase inhibitor) leads to the dephosphorylation of CPERMs, the translocation of ERM proteins from plasma membranes to the cytoplasm and microvillar breakdown. We further elucidated that ERM protein activation does not require C-terminal phosphorylation in A431 cells stimulated with epidermal growth factor. In certain types of kidney-derived cells such as MDCK cells, however, ERM proteins appear to be activated in the absence of Rho activation and remain active without C-terminal phosphorylation. Interestingly, microinjection of an aminoglycoside antibiotic, neomycin, which binds to polyphosphoinositides, such as phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P(2)], affected the activation of ERM proteins regardless of cell type. These findings not only indicate the existence of a Rho-independent activation mechanism of ERM proteins but also suggest that both Rho-dependent and -independent activation of ERM proteins require a local elevation of PtdIns(4,5)P(2) concentration in vivo.
Volume 115(Pt 12)
Pages 2569-80
Published 2002-6-15
DOI 10.1242/jcs.115.12.2569
PMID 12045227
MeSH 3T3 Cells ADP Ribose Transferases / pharmacology Animals Blood Proteins / metabolism* Botulinum Toxins / pharmacology CHO Cells Cell Membrane / metabolism Cell Membrane / ultrastructure Cricetinae Cytoskeletal Proteins / metabolism* Cytoskeleton / metabolism* Cytoskeleton / ultrastructure Epidermal Growth Factor / pharmacology Eukaryotic Cells / metabolism Eukaryotic Cells / ultrastructure Fluorescent Antibody Technique HeLa Cells Humans Membrane Proteins / metabolism* Mice Microfilament Proteins / metabolism* Microscopy, Electron Microvilli / metabolism* Microvilli / ultrastructure Phosphatidylinositols / metabolism* Phosphoproteins / metabolism* Protein Structure, Tertiary / drug effects Protein Structure, Tertiary / physiology Protein Transport / drug effects Protein Transport / physiology rho GTP-Binding Proteins / metabolism*
IF 4.573
Times Cited 196
Human and Animal Cells