Carom: a novel membrane-associated guanylate kinase-interacting protein with two SH3 domains

Abstract

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.

Genome-wide association study of Crohn's disease in Koreans revealed three new susceptibility loci and common attributes of genetic susceptibility across ethnic populations

“…rs11235667 is within a LD region of ∼430 kb that includes FCHSD2, ATG16L2 and STARD10. FCHSD2 (FCH and double SH3 domains 2) has a coiled-coil domain followed by two SH3 domains and the PDZ-binding motif at the C terminus and was shown to interact with membrane-associated guanylate kinases of epithelial junctions 49. From the eQTL databases, marginal significance was observed between rs11235667 and mRNA expression of ATG16L2 (p=0.042) in HapMap3 (CHB) derived lymphoblastoid cell lines (see online supplementary table S5).…”

The Role of the MAGUK Protein CASK in Neural Development and Synaptic Function

“…Because the important residues at the active site are mutated, the CaMK-like domain of CASK is not expected to have kinase activity [4]. Instead, the CASK CaMK-like domain functions as a protein-protein interacting domain, which binds to several cellular proteins, such as Mint1/X11 [13,14], Caskin 1 [15], CIP98 [16], and Carom [17]. The function of the interaction between CASK and CIP98 or Carom is unclear.…”

MAGI-1 is a component of the glomerular slit diaphragm that is tightly associated with nephrin

“…pCIneoMyc MAGI-1-I, -II, -III, -IV, -V, pCIneoMyc ZO-1-1, pFLAG-JAM4, and pGex4T-1 JAM4-C were described previously. 25,30,31 Human cDNA of nephrin was obtained by PCR using primers (5 0 -aagcttttggcgattcctgcctccgtt-3 0 and 5 0 -gtcgactacaccagatgtcccctcagctc-3 0 ) on human kidney cDNA (BioChain, Inc.). The following constructs were made using pGex4T-1 (Amersham Pharmacia Biotech) and pFLAG-CMV-1 (Eastman Kodak Company) and encoded the corresponding amino acids of human nephrin or human MAGI-1: pFLAG nephrin, amino acids 24-1241; pFLAG nephrin-del C, 24-1236; pGex4T-1 nephrin-C, 1087-1241 of nephrin; pGex4T-1 nephrin-C del, 1087-1236; pBTM116 KM MAGI-1-8, 430-1256; pGex4T-1 MAGI-1-A, 565-994; pGex4T-1 MAGI-1-B, 565-836; pGex4T-1 MAGI-1-C, 771-994; pGex4T-1 MAGI-1-D, 565-865; pGex4T-1 MAGI-1-E, 697-994; pGex4T-1 MAGI-1-F, 697-865.…”