Mammalian Scribble forms a tight complex with the betaPIX exchange factor.
Drosophila Scribble is implicated in the development of normal synapse structure and epithelial tissues, but it remains unclear how it plays a role and which process it controls. The mammalian homolog of Scribble, hScrib, has a primary structure and subcellular localization similar to that of its fly homolog, but its function remains unknown. Here we have used tandem mass spectrometry to identify major components of the hScrib network. We show that it includes betaPIX (also called Cool-1), a guanine nucleotide exchange factor (GEF), and its partner GIT1 (also called p95-APP1), a GTPase activating protein (GAP). betaPIX directly binds to the hScrib PDZ domains, and the hScrib/betaPIX complex is efficiently recovered in epithelial and neuronal cells and tissues. In cerebellar granule cell cultures, hScrib and betaPIX are both partially localized at neuronal presynaptic compartments. Furthermore, we show that hScrib is required to anchor betaPIX at the cell cortex and that dominant-negative betaPIX or hScrib proteins can each inhibit Ca2+-dependent exocytosis in neuroendocrine PC12 cells, demonstrating a functional relationship between these proteins. These data reveal the existence of a tight hScrib/betaPIX interaction and suggest that this complex potentially plays a role in neuronal transmission.
Audebert
Stéphane
S
Molecular Pharmacology, Institut de Recherches sur le Cancer de Marseille, Unite mixte de recherche 599 Inserm-Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France.
Navarro
Christel
C
Nourry
Claire
C
Chasserot-Golaz
Sylvette
S
Lécine
Patrick
P
Bellaiche
Yohanns
Y
Dupont
Jean-Luc
JL
Premont
Richard T
RT
Sempéré
Christine
C
Strub
Jean-Marc
JM
Van Dorsselaer
Alain
A
Vitale
Nicolas
N
Borg
Jean-Paul
JP
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005089:Exocytosis / Q000187:drug effects; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000378:metabolism* / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D017729:Presynaptic Terminals / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064067:Rho Guanine Nucleotide Exchange Factors; D025521:Tumor Suppressor Proteins; D020798:Two-Hybrid System Techniques
C576606:ARHGEF7 protein, human; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; C485647:GIT1 protein, human; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D010750:Phosphoproteins; D064067:Rho Guanine Nucleotide Exchange Factors; C480591:SCRIB protein, human; D025521:Tumor Suppressor Proteins