MAGI-3 competes with NHERF-2 to negatively regulate LPA2 receptor signaling in colon cancer cells.
OBJECTIVE
Lysophosphatidic acid (LPA) is a potent inducer of colon cancer and LPA receptor type 2 (LPA(2)) is overexpressed in colon tumors. LPA(2) interacts with membrane-associated guanylate kinase with inverted orientation-3 (MAGI-3) and the Na+/H+ exchanger regulatory factor 2 (NHERF-2), but the biological effects of these interactions are unknown. We investigated the roles of MAGI-3 and NHERF-2 in LPA(2)-mediated signaling in human colon cancer cells.


METHODS
We overexpressed or knocked down MAGI-3 in HCT116 and SW480 cells. The effects of MAGI-3 and NHERF-2 in LPA-induced cell migration, invasion, inositol phosphate generation, and nuclear factor-κB activation were determined. Expression of MAGI-3 and NHERF-2 in human colon tumor tissues was analyzed using tissue microarray analysis.


RESULTS
NHERF-2 promoted migration and invasion of colon cancer cells, whereas MAGI-3 inhibited these processes. MAGI-3 competed with NHERF-2 for binding to LPA(2) and phospholipase C-β3. However, NHERF-2 and MAGI-3 reciprocally regulated LPA(2)-induced phospholipase C activity. MAGI-3 increased the interaction of LPA(2) with Gα(12), whereas NHERF-2 preferentially promoted interaction between LPA(2) and Gα(q). MAGI-3 decreased the tumorigenic capacity of LPA(2) by attenuating the activities of nuclear factor-κB and c-Jun N-terminal kinase. MAGI-3 and NHERF-2 were expressed differentially in colon adenocarcinomas, consistent with their opposing effects.


CONCLUSIONS
LPA(2) is dynamically regulated by 2 distinct PDZ proteins via modulation of G-protein coupling and receptor signaling. MAGI-3 is a negative regulator of LPA(2) signaling.
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Sei-Jung
SJ
Lee
Stefanie L
SL
Ritter
Huanchun
H
Zhang
Hyunsuk
H
Shim
Randy A
RA
Hall
C Chris
CC
Yun
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011125:Adenomatous Polyposis Coli / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002465:Cell Movement; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D017491:Genes, APC; D045325:HCT116 Cells; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008246:Lysophospholipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D009361:Neoplasm Invasiveness; D054799:Phospholipase C beta / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D046888:Tissue Array Analysis; D014162:Transfection
D007295:Inositol Phosphates; D008246:Lysophospholipids; C496469:MAGI3 protein, human; D008565:Membrane Proteins; D016328:NF-kappa B; D010750:Phosphoproteins; D049368:Receptors, Lysophosphatidic Acid; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D048031:JNK Mitogen-Activated Protein Kinases; C518039:PLCB3 protein, human; D054799:Phospholipase C beta; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C032881:lysophosphatidic acid