The diaphanous-related formin DAAM1 collaborates with the Rho GTPases RhoA and Cdc42, CIP4 and Src in regulating cell morphogenesis and actin dynamics.
Binding partners for the Cdc42 effector CIP4 were identified by the yeast two-hybrid system, as well as by testing potential CIP4-binding proteins in coimmunoprecipitation experiments. One of the CIP4-binding proteins, DAAM1, was characterised in more detail. DAAM1 is a ubiquitously expressed member of the mammalian diaphanous-related formins, which include proteins such as mDia1 and mDia2. DAAM1 was shown to bind to the SH3 domain of CIP4 in vivo. Ectopically expressed DAAM1 localised in dotted pattern at the dorsal side of transfected cells and the protein was accumulated in the proximity to the microtubule organising centre. Moreover, ectopic expression of DAAM1 induced a marked alteration of the cell morphology, seen as rounding up of the cells, the formation of branched protrusions as well as a reduction of stress-fibres in the transfected cells. Coimmunoprecipitation experiments demonstrated that DAAM1 bound to RhoA and Cdc42 in a GTP-dependent manner. Moreover, DAAM1 was found to interact and collaborate with the non-receptor tyrosine kinase Src in the formation of branched protrusions. Taken together, our data indicate that DAAM1 communicates with Rho GTPases, CIP4 and Src in the regulation of the signalling pathways that co-ordinate the dynamics of the actin filament system.
Aspenström
Pontus
P
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala University, Box 595, S-751 24 Uppsala, Sweden. pontus.aspenstrom@licr.uu.se
Richnau
Ninna
N
Johansson
Ann-Sofi
AS
D008841:Actin Cytoskeleton / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D048430:Cell Shape / Q000502:physiology*; D022081:Cell Surface Extensions / Q000502:physiology; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D000080865:Formins; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D008954:Models, Biological; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000235:genetics / Q000502:physiology; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C499094:DAAM1 protein, human; C491464:Diap1 protein, mouse; D000080865:Formins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D015778:Minor Histocompatibility Antigens; C406285:TRIP10 protein, human; C508552:Dia2 protein, mouse; D009252:NADPH Dehydrogenase; D020797:Receptor, Platelet-Derived Growth Factor beta; D019061:src-Family Kinases; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein