Association of Calnexin with Wild Type and Mutant AVPR2 that Cause Nephrogenic Diabetes Insipidus
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- 作者：Jean-Pierre Morello ; Ali Salahpour ; Ulla E. Petä ; jä ; -Repo ; André ; Laperriè ; re ; Michè ; le Lonergan ; Marie-Franç ; oise Arthus ; Ivan R. Nabi ; Daniel G. Bichet ; and Michel Bo
- 刊名：Biochemistry
- 出版年：2001
- 出版时间：June 12, 2001
- 年：2001
- 卷：40
- 期：23
- 页码：6766 - 6775
- 全文大小：640K
- 年卷期：v.40,no.23(June 12, 2001)
- ISSN：1520-4995
文摘
Over 155 mutations within the V2 vasopressin receptor (AVPR2) gene are responsible fornephrogenic diabetes insipidus (NDI). The expression and subcellular distribution of four of these wasinvestigated in transfected cells. These include a point mutation in the seventh transmembrane domain(S315R), a frameshift mutation in the third intracellular loop (804delG), and two nonsense mutations thatcode for AVPR2 truncated within the first cytoplasmic loop (W71X) and in the proximal portion of thecarboxyl tail (R337X). RT-PCR revealed that mRNA was produced for all mutant receptor constructs.However, no receptor protein, as assessed by Western blot analysis, was detected for 804delG. The S315Rwas properly processed through the Golgi and targeted to the plasma membrane but lacked any detectableAVP binding or signaling. Thus, this mutation induces a conformational change that is compatible withendoplasmic reticulum (ER) export but dramatically affects hormone recognition. In contrast, the W71Xand R337X AVPR2 were retained inside the cell as determined by immunofluorescence. Confocalmicroscopy revealed that they were both retained in the ER. To determine if calnexin could be involved,its interaction with the AVPR2 was assessed. Sequential coimmunoprecipitation demonstrated that calnexinassociated with the precursor forms of both wild-type (WT) and mutant receptors in agreement with itsgeneral role in protein folding. Moreover, its association with the ER-retained R337X mutant was foundto be longer than with the WT receptor suggesting that this molecular chaperone also plays a role inquality control and ER retention of misfolded G protein-coupled receptors.