High Affinity Interaction with Filamin A Protects against Calcium-sensing Receptor Degradation

• Published in: The Journal of biological chemistry Vol. 280; no. 12; pp. 11140 - 11146
• Main Authors: Zhang, Mingliang, Breitwieser, Gerda E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.03.2005; American Society for Biochemistry and Molecular Biology
• Subjects: Cell Line; Cell Membrane - metabolism; Contractile Proteins - chemistry; Contractile Proteins - physiology; Filamins; Humans; MAP Kinase Signaling System; Microfilament Proteins - chemistry; Microfilament Proteins - physiology; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; Receptors, Calcium-Sensing - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M412242200

Calcium-sensing receptors (CaR) regulate cell proliferation, differentiation, and apoptosis through the MAPK pathway. MAPK pathway activation requires the cytoskeletal scaffold protein filamin A. Here we examine the interactions of CaR with filamin A in HEK-293 and M2 or A7 melanoma cells to determine how interactions with filamin A facilitate signaling. Filamin A interacts with CaR through two predicted β-strands from residues 962 to 981; interactions between filamin A and CaR are greatly enhanced by exposure to 5 mm Ca2+. Truncations or deletions (from 972 to 997 or 962 to 981) of the CaR carboxyl terminus eliminate high affinity interactions with filamin A, but CaR-mediated MAPK pathway activation still occurs. CaR-mediated ERK phosphorylation can be localized to a predicted α-helix proximal to the membrane, which has been shown to be important for G protein-mediated signaling (residues 868–879). In M2 cells (–filamin A), CaR expression levels are very low; cotransfection of CaR with filamin A increases total cellular CaR and increases plasma membrane localization of CaR, facilitating CaR signaling to the MAPK pathway; similar results were obtained in HEK-293 cells. Interaction with filamin A increases cellular CaR by preventing CaR degradation, thereby facilitating CaR signaling. In addition, filamin A facilitates signaling to the MAPK pathway even by CaR truncations or deletion mutants that cannot engage in high affinity interactions with filamin A, suggesting the targeting of critical signaling proteins to CaR.