Proproliferative and antiapoptotic action of exogenously introduced YAP in pancreatic β cells
Ting Yuan, Sahar Rafizadeh, Zahra Azizi, Blaz Lupse, Kanaka Durga Devi Gorrepati, Sushil Awal, Jose Oberholzer, Kathrin Maedler, Amin Ardestani
Ting Yuan, Sahar Rafizadeh, Zahra Azizi, Blaz Lupse, Kanaka Durga Devi Gorrepati, Sushil Awal, Jose Oberholzer, Kathrin Maedler, Amin Ardestani
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Research Article Cell biology Endocrinology

Proproliferative and antiapoptotic action of exogenously introduced YAP in pancreatic β cells

Abstract

Loss of functional pancreatic β cells is a hallmark of both type 1 and 2 diabetes. Identifying the pathways that promote β cell proliferation and/or block β cell apoptosis is a potential strategy for diabetes therapy. The transcriptional coactivator Yes-associated protein (YAP), a major downstream effector of the Hippo signaling pathway, is a key regulator of organ size and tissue homeostasis by modulating cell proliferation and apoptosis. YAP is not expressed in mature primary human and mouse β cells. We aimed to identify whether reexpression of a constitutively active form of YAP promotes β cell proliferation/survival. Overexpression of YAP remarkably induced β cell proliferation in isolated human islets, while β cell function and functional identity genes were fully preserved. The transcription factor forkhead box M1 (FOXM1) was upregulated upon YAP overexpression and necessary for YAP-dependent β cell proliferation. YAP overexpression protected β cells from apoptosis triggered by multiple diabetic conditions. The small redox proteins thioredoxin-1 and thioredoxin-2 (Trx1/2) were upregulated by YAP; disruption of the Trx system revealed that Trx1/2 was required for the antiapoptotic action of YAP in insulin-producing β cells. Our data show the robust proproliferative and antiapoptotic function of YAP in pancreatic β cells. YAP reconstitution may represent a disease-modifying approach to restore a functional β cell mass in diabetes.

Authors

Ting Yuan, Sahar Rafizadeh, Zahra Azizi, Blaz Lupse, Kanaka Durga Devi Gorrepati, Sushil Awal, Jose Oberholzer, Kathrin Maedler, Amin Ardestani

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Figure 6

Antiapoptotic effect of YAP is mediated by redox proteins Trx1/2.

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Antiapoptotic effect of YAP is mediated by redox proteins Trx1/2. (A, C,...
(A, C, and D) INS-1E cells were transfected with either control GFP or YAP plasmid for 2 days. (A) Trx1 and Trx2 gene expression was analyzed by RT-PCR and levels normalized to actin and shown as change from GFP-transfected cells. Pooled data from 3 independent experiments (n = 3). (C and D) Representative Western blots (C) and quantitative densitometry analysis (D) of Trx1 and Trx2 protein levels are shown. Both lanes were run in the same gel but were noncontiguous. Pooled data from 4 independent experiments (n = 4). (B, E, and F) Human islets were infected with either control adenovirus expressing luciferase (Ad-Luc) or Ad-YAP for 2 days. (B) Trx1 and Trx2 gene expression was analyzed by RT-PCR and levels normalized to tubulin and shown as change from Ad-Luc–infected human islets. Pooled data from 3 independent experiments from 3 human islet donors (n = 3). (E and F) Representative Western blots (E) and quantitative densitometry analysis (F) of Trx1 and Trx2 protein levels are shown. Pooled data from 4 independent experiments from 4 different human islet donors (n = 4). Flag and GAPDH blots in E are reused from human islet number 3 in Figure 2B. (G) INS-1E cells were transfected with either control GFP or YAP plasmids and treated with 22.2 mM glucose (HG) for 2 days. PX-12 (Trx1 inhibitor) and auranofin (thioredoxin reductase inhibitor) were added for the last 24 hours. (H) INS-1E cells were transfected with either control GFP or YAP and scrambled control siRNA (siScr) or Trx1 or Trx2 siRNA and treated with 22.2 mM glucose (HG) for 2 days. All lanes were run in the same gel but were noncontiguous. Western blots show representative results from 3 independent experiments (n = 3). Data are the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 for YAP compared with control GFP- or Luc- transfected/infected conditions by 2-tailed Student’s t test.