Borg proteins control septin organization and are negatively regulated by Cdc42.
The Cdc42 GTPase binds to numerous effector proteins that control cell polarity, cytoskeletal remodelling and vesicle transport. In many cases the signalling pathways downstream of these effectors are not known. Here we show that the Cdc42 effectors Borg1 to Borg3 bind to septin GTPases. Endogenous septin Cdc10 and Borg3 proteins can be immunoprecipitated together by an anti-Borg3 antibody. The ectopic expression of Borgs disrupts normal septin organization. Cdc42 negatively regulates this effect and inhibits the binding of Borg3 to septins. Borgs are therefore the first known regulators of mammalian septin organization and provide an unexpected link between the septin and Cdc42 GTPases.
Joberty
G
G
Markey Center for Cell Signaling and Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA. gmj4h@virginia.edu
Perlungher
R R
RR
Sheffield
P J
PJ
Kinoshita
M
M
Noda
M
M
Haystead
T
T
Macara
I G
IG
D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D003598:Cytoskeletal Proteins; D020549:GTP Phosphohydrolase Activators; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020555:GTP-Binding Protein Regulators; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020741:rho GTP-Binding Proteins
D001798:Blood Proteins; C422984:CDC42EP2 protein, human; C422985:CDC42EP4 protein, human; C484092:Cdc42ep5 protein, mouse; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D020549:GTP Phosphohydrolase Activators; D020555:GTP-Binding Protein Regulators; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins