Interaction between two adapter proteins, PAG and EBP50: a possible link between membrane rafts and actin cytoskeleton

Abstract

Phosphoprotein associated with GEMs (PAG), also known as Csk-binding protein (Cbp), is a broadly expressed palmitoylated transmembrane adapter protein found in membrane rafts, also called GEMs (glycosphingolipid-enriched membrane microdomains). PAG is known to bind and activate the essential regulator of Src-family kinases, cytoplasmic protein tyrosine kinase Csk. In the present study we used the yeast 2-hybrid system to search for additional proteins which might bind to PAG. We have identified the abundant cytoplasmic adapter protein EBP50 (ezrin/radixin/moesin (ERM)-binding phosphoprotein of 50 kDa), also known as NHERF (Na + /H + exchanger regulatory factor), as a specific PAG-binding partner. The interaction involves the C-terminal sequence (TRL) of PAG and N-terminal PDZ domain(s) of EBP50. As EBP50 is known to interact via its C-terminal domain with the ERM-family proteins, which in turn bind to actin cytoskeleton, the PAGÊ BP50 interaction may be important for connecting membrane rafts to the actin cytoskeleton. ß 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

A macromolecular complex of β 2 adrenergic receptor, CFTR, and ezrin/radixin/moesin-binding phosphoprotein 50 is regulated by PKA

“…This result has been clearly demonstrated for the ␤ adrenergic receptor, as stimulation of the human airway mucosa with the nonspecific ␤ receptor agonist isoproterenol activates CFTR-dependent Cl Ϫ transport in vivo (6). Biochemical studies have demonstrated that the C-termini of CFTR and ␤ 2 adrenergic receptors (␤ 2 AR) possess PDZ binding motifs, and these domains contribute to interactions between these membrane proteins (7-9) and cytoskeletal proteins (10) that are important for channel regulation (11,12) and trafficking (13,14). No studies, however, have conclusively demonstrated that interactions of this sort contribute to CFTR regulation by surface receptors.…”

Nanotubes connecting B lymphocytes: High impact of differentiation-dependent lipid composition on their growth and mechanics

“…Thus, lipid rafts can control NT growth in a different way, as well. In lymphoid cells, the PM rafts usually contain raft-associated adaptor membrane proteins, such as PAG or EBP50 ezrin-binding protein, that may mediate dynamic connections of the PM to the actin filament network [53,54]. Binding of pleckstrin homology domain proteins is also under control of cholesterol level and thus responsible for the dynamic coupling to the actin cytoskeleton [15].…”

Overexpression of Csk-binding protein contributes to renal cell carcinogenesis

“…The PDZ-binding motif of Cbp may mediate the regulation of RhoA activation Cbp is known to interact via its C-terminal PDZbinding motif with EBP50, which in turn binds to ERM family (Brdickova et al, 2001;Itoh et al, 2002). ERM proteins have been implicated in the regulation of cytoskeleton organization and Rho GTPases activation (Bretscher, 1999;D'Angelo et al, 2007;Niggli and Rossy, 2008).…”

“…Here, we found that the PDZ-binding motif of Cbp might be associated with RhoA activation. Cbp is well known to bind to EBP50 via this PDZ-binding motif (Brdickova et al, 2001;Itoh et al, 2002). EBP50 is a cytosolic protein that links membrane proteins with ERM proteins, which directly interact with actin cytoskeletons once activated (Reczek et al, 1997;Bretscher, 1999).…”

“…Besides the classical SFKs activities regulation, Cbp is implicated in some other pathways as yeast two-hybrid analysis demonstrated that Cbp binds to EBP50 (ezrin/ radixin/moesin (ERM)-binding phosphoprotein of 50 kDa), an cytosolic adaptor protein that associates with ERM proteins (Brdickova et al, 2001;Itoh et al, 2002). Although it has been shown that Cbp negatively regulates T-cell activation by interacting with EBP50 (Itoh et al, 2002), the precise mechanism and biological significance of this interaction in other systems remain to be clarified.…”