PMID- 22090276 OWN - NLM STAT- MEDLINE DCOM- 20120409 LR - 20161125 IS - 1945-7197 (Electronic) IS - 0021-972X (Linking) VI - 97 IP - 2 DP - 2012 Feb TI - Menin missense mutants encoded by the MEN1 gene that are targeted to the proteasome: restoration of expression and activity by CHIP siRNA. PG - E282-91 LID - 10.1210/jc.2011-0241 [doi] AB - CONTEXT: In multiple endocrine neoplasia type 1 (MEN1) characterized by tumors of parathyroid, enteropancreas, and anterior pituitary, missense mutations in the MEN1 gene product, menin, occur in a subset of cases. The mutant proteins are degraded by the proteasome. However, whether their expression and activity can be restored is not known. OBJECTIVE: Our objective was to functionally characterize a panel of 16 menin missense mutants, including W423R and S443Y identified in new MEN1 families, with respect to protein stability, targeting to the proteasome and restoration of expression by proteasome inhibitors and expression and function by small interfering RNA technology. METHODS: Flag-tagged wild-type (WT) and missense menin mutant expression vectors were transiently transfected in human embryonic kidney (HEK293) and/or rat insulinoma (Rin-5F) cells. RESULTS: The majority of mutants were short-lived, whereas WT menin was stable. Proteasome inhibitors MG132 and PS-341 and inhibition of the chaperone, heat-shock protein 70 (Hsp70), or the ubiquitin ligase, COOH terminus of Hsp70-interacting protein (CHIP), by specific small interfering RNA, restored the levels of the mutants, whereas that of WT menin was largely unaffected. Inhibition of CHIP restored the ability of mutants to mediate normal functions of menin: TGF-beta up-regulation of the promoters of its target genes, the cyclin-dependent kinase inhibitors p15 and p21 as well as TGF-beta inhibition of cell numbers. CONCLUSION: When the levels of missense menin mutants that are targeted to the proteasome are normalized they may function similarly to WT menin. Potentially, targeting specific components of the proteasome chaperone pathway could be beneficial in treating a subset of MEN1 cases. FAU - Canaff, Lucie AU - Canaff L AD - Department of Medicine, Calcium Research Laboratory, and Hormones and Cancer Research Unit, Royal Victoria Hospital, McGill University, Montreal, Quebec H3A 1A1, Canada. FAU - Vanbellinghen, Jean-Francois AU - Vanbellinghen JF FAU - Kanazawa, Ippei AU - Kanazawa I FAU - Kwak, Hayeon AU - Kwak H FAU - Garfield, Natasha AU - Garfield N FAU - Vautour, Line AU - Vautour L FAU - Hendy, Geoffrey N AU - Hendy GN LA - eng GR - MOP-9315/Canadian Institutes of Health Research/Canada PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20111116 PL - United States TA - J Clin Endocrinol Metab JT - The Journal of clinical endocrinology and metabolism JID - 0375362 RN - 0 (MEN1 protein, human) RN - 0 (Mutant Proteins) RN - 0 (Proto-Oncogene Proteins) RN - 0 (RNA, Small Interfering) RN - EC 2.3.2.27 (STUB1 protein, human) RN - EC 2.3.2.27 (Ubiquitin-Protein Ligases) RN - EC 3.4.25.1 (Proteasome Endopeptidase Complex) SB - IM MH - Animals MH - Enzyme Activation/drug effects/genetics MH - Family MH - Gene Expression Regulation/drug effects MH - HEK293 Cells MH - Humans MH - Mutant Proteins/genetics/metabolism MH - Mutation, Missense/physiology MH - Proteasome Endopeptidase Complex/drug effects/*metabolism/physiology MH - Protein Transport/drug effects/genetics MH - Proteolysis/drug effects MH - Proto-Oncogene Proteins/*genetics/*metabolism MH - RNA, Small Interfering/*pharmacology MH - Rats MH - Tumor Cells, Cultured MH - Ubiquitin-Protein Ligases/*antagonists & inhibitors/genetics EDAT- 2011/11/18 06:00 MHDA- 2012/04/10 06:00 CRDT- 2011/11/18 06:00 PHST- 2011/11/18 06:00 [entrez] PHST- 2011/11/18 06:00 [pubmed] PHST- 2012/04/10 06:00 [medline] AID - jc.2011-0241 [pii] AID - 10.1210/jc.2011-0241 [doi] PST - ppublish SO - J Clin Endocrinol Metab. 2012 Feb;97(2):E282-91. doi: 10.1210/jc.2011-0241. Epub 2011 Nov 16.