Dominant protein interactions that influence the pathogenesis of conformational diseases
Jordan Wright, … , Ming Liu, Peter Arvan
Jordan Wright, … , Ming Liu, Peter Arvan
Published June 3, 2013
Citation Information: J Clin Invest. 2013;123(7):3124-3134. https://doi.org/10.1172/JCI67260.
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Research Article Endocrinology

Dominant protein interactions that influence the pathogenesis of conformational diseases

Abstract

Misfolding of exportable proteins can trigger endocrinopathies. For example, misfolding of insulin can result in autosomal dominant mutant INS gene–induced diabetes of youth, and misfolding of thyroglobulin can result in autosomal recessive congenital hypothyroidism with deficient thyroglobulin. Both proinsulin and thyroglobulin normally form homodimers; the mutant versions of both proteins misfold in the ER, triggering ER stress, and, in both cases, heterozygosity creates potential for cross-dimerization between mutant and WT gene products. Here, we investigated these two ER-retained mutant secretory proteins and the selectivity of their interactions with their respective WT counterparts. In both cases and in animal models of these diseases, we found that conditions favoring an increased stoichiometry of mutant gene product dominantly inhibited export of the WT partner, while increased relative level of the WT gene product helped to rescue secretion of the mutant partner. Surprisingly, the bidirectional consequences of secretory blockade and rescue occur simultaneously in the same cells. Thus, in the context of heterozygosity, expression level and stability of WT subunits may be a critical factor influencing the effect of protein misfolding on clinical phenotype. These results offer new insight into dominant as well as recessive inheritance of conformational diseases and offer opportunities for the development of new therapies.

Authors

Jordan Wright, Xiaofan Wang, Leena Haataja, Aaron P. Kellogg, Jaemin Lee, Ming Liu, Peter Arvan

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Figure 4

Cross-dimerization as a basis for secretory rescue of mutant proinsulin or Tg is specific to respective WT partners.

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Cross-dimerization as a basis for secretory rescue of mutant proinsulin ...
(A) 293T cells transiently expressing both mutant proinsulin and mutant Tg were cotransfected with either WT mPro or WT Tg. The media were collected overnight, and cells were lysed; proinsulin secretion was quantified by hPro-specific RIA. Data represent mean ± SEM relative to cells lacking mPro or WT Tg (P = 0.07, n = 3). From the same cell lysates and media, secretion of rdw-TgGFP was analyzed by SDS-PAGE, electrotransfer, and immunoblotting with anti-GFP. (B) At 48 hours after cotransfection, overnight secretion of mutant hProG(B23)V-CpepMyc (in duplicate) was measured by immunoprecipitation and immunoblotting with anti-Myc. The results shown in A and B are representative of 3 separate experiments. EV, empty vector. (C) At 48 hours after transfection, cells cotransfected as indicated were either untreated or treated with 5 μg/ml brefeldin A (BFA). After 5 hours, the media were collected and analyzed by hPro-specific RIA. The data shown are mean values ± range from 2 independent measurements.