The PDZ domain protein CAL interacts with mGluR5a and modulates receptor expression.
In this study, we investigated the association of metabotropic glutamate receptor subtype-5a (mGluR5a) with cystic fibrosis transmembrane conductance regulator-associated ligand (CAL). Using glutathione-S-transferase pull-down techniques, we found that mGluR5a directly interacted with CAL, with the C-terminus of the receptor binding to the PSD95/Discslarge/ZO-1 homology domain of CAL. The last four amino acids (S-S-S-L) of the C-terminus of the receptor were essential determinants for the interaction. Co-immunoprecipitation experiments and immunofluorescence assays revealed that full-length mGluR5a also associated with intact CAL in vivo, an observation consistent with the results from studies on fragment interactions in vitro. Functionally, upon co-expression with mGluR5a, CAL profoundly inhibited the ubiquitination of mGluR5a and enhanced receptor expression at the protein level but not at the mRNA level. These findings reveal that mGluR5a protein expression is physiologically regulated via its interaction with CAL. These results also suggest a molecular mechanism by which mGluR5a protein expression may be regulated at the post-translational level by the CAL protein, possibly by blocking ubiquitination-dependent receptor degradation.
Cheng
Shan
S
Department of Biochemistry and Molecular Biology, Capital Medical University, Beijing 100069, China.
Zhang
Jiuqin
J
Zhu
Ping
P
Ma
Yanmei
Y
Xiong
Ying
Y
Sun
Licui
L
Xu
Jianguo
J
Zhang
Hong
H
He
Junqi
J
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D002522:Chlorocebus aethiops; D006224:Cricetinae; D015870:Gene Expression / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D000077614:Golgi Matrix Proteins; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D014162:Transfection / Q000379:methods
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C434484:GOPC protein, human; C578935:GRM5 protein, human; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D034741:RNA, Small Interfering; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate