Carom: a novel membrane-associated guanylate kinase-interacting protein with two SH3 domains.
MAGI-1 and CASK are membrane-associated guanylate kinases of epithelial junctions. MAGI-1 is localized at tight junctions in polarized epithelial cells, whereas CASK is localized along the lateral membranes. We obtained the KIAA0769 gene product through the yeast two-hybrid screening using MAGI-1 as a bait and named it Carom. Carom has a coiled-coil domain in the middle region, and two src homology 3 domains and a PSD-95/Dlg-A/ZO-1 (PDZ)-binding motif in the C-terminal region. Carom binds to the fifth PDZ domain of MAGI-1 and the calmodulin kinase domain of CASK in vitro. MAGI-1 and CASK bind to the distinct sequences in the C-terminal region of Carom, but still compete with each other for Carom binding. The study using a stable transformant of Madine Darby canine kidney (MDCK) cells expressing GFP-Carom revealed that Carom was partially overlapped by MAGI-1 in MDCK cells, which have not yet established mature cell junctions, but became separated from MAGI-1 and colocalized with CASK in polarized cells. Carom was highly resistant to Triton X-100 extractions and recruited CASK to the Triton X-100-insoluble structures. Carom is a binding partner of CASK, which interacts with CASK in polarized epithelial cells and may link it to the cytoskeleton.
Ohno
Hideki
H
Department of Medical Biochemistry, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
Hirabayashi
Susumu
S
Kansaku
Ai
A
Yao
Ikuko
I
Tajima
Makiko
M
Nishimura
Wataru
W
Ohnishi
Hirohide
H
Mashima
Hirosato
H
Fujita
Toshiro
T
Omata
Masao
M
Hata
Yutaka
Y
D000818:Animals; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D051528:Guanylate Kinases; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D009928:Organ Specificity; D017434:Protein Structure, Tertiary; D051381:Rats; D020539:Sequence Analysis, Protein; D019108:Tight Junctions / Q000378:metabolism
D002352:Carrier Proteins; C479761:FCHSD2 protein, human; D008565:Membrane Proteins; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases