MAGI-3 competes with NHERF-2 to negatively regulate LPA2 receptor signaling in colon cancer cells

Background & aims: 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.