Recruitment of Dbl by ezrin and dystroglycan drives membrane proximal Cdc42 activation and filopodia formation.
Dystroglycan is an essential laminin binding cell adhesion molecule, which is also an adaptor for several SH2 domain-containing signaling molecules and as a scaffold for the ERK-MAP kinase cascade. Loss of dystroglycan function is implicated in muscular dystrophies and the aetiology of epithelial cancers. We have previously demonstrated a role for dystroglycan and ezrin in the formation of filopodia structures. Here we demonstrate the existence of a dystroglycan:ezrin:Dbl complex that is targeted to the membrane by dystroglycan where it drives local Cdc42 activation and the formation of filopodia. Deletion of an ezrin binding site in dystroglycan prevented the association with ezrin and Dbl and the formation of filopodia. Furthermore, expression of the dystroglycan cytoplasmic domain alone had a dominant-negative effect on filopodia formation and Cdc42 activation by sequestering ezrin and Dbl away from the membrane. Depletion of dystroglycan inhibited Cdc42-induced filopodia formation. For the first time we also demonstrate co-localization of Cdc42 and dystroglycan at the tips of dynamic filopodia.
Batchelor
Clare L
CL
Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield, UK.
Higginson
Jen R
JR
Chen
Yun-Ju
YJ
Vanni
Cristina
C
Eva
Alessandra
A
Winder
Steve J
SJ
D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D049030:Dystroglycans / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D051379:Mice; D009154:Mutation; D011485:Protein Binding; D011554:Pseudopodia / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D041701:Swiss 3T3 Cells; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D000099149:Ezrin
D000199:Actins; D003598:Cytoskeletal Proteins; D049030:Dystroglycans; D049452:Green Fluorescent Proteins; D020662:Guanine Nucleotide Exchange Factors; D011993:Recombinant Fusion Proteins; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D000099149:Ezrin