JNK and p53 cause human and mouse β cell death during excessive unfolded protein response
Rohit B. Sharma, Christine Darko, Ying Wang, Thalia A. Castro, Tara Doma Lama, Brian Gablaski, Andrew Rappa, David Redmond, Jason K. Kim, Amy S. Lee, Laura C. Alonso
Rohit B. Sharma, Christine Darko, Ying Wang, Thalia A. Castro, Tara Doma Lama, Brian Gablaski, Andrew Rappa, David Redmond, Jason K. Kim, Amy S. Lee, Laura C. Alonso
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Research Article Endocrinology Metabolism

JNK and p53 cause human and mouse β cell death during excessive unfolded protein response

Abstract

Endoplasmic reticulum (ER) stress contributes to β cell death in both Type 1 and Type 2 diabetes (T1D and T2D). However, the molecular mechanisms driving β cell death during ER stress remain insufficiently defined, limiting development of protective therapies. GRP78, an ER chaperone, is the master regulator of unfolded protein response (UPR), suppressing UPR initiators during the unstressed state and releasing them to allow UPR activation during stress. To dissect the pathways leading to ER-stress response related β cell decompensation, we engineered mice genetically lacking GRP78 in pancreatic β cells. GRP78 deletion caused acute insulin-deficient diabetes in pups before weaning, with reduced β cell mass due to increased apoptosis. Molecular studies identified deregulated UPR, specifically IRE1 activity, as driving cell death. Unbiased and targeted analyses identified a JNK-p53 axis downstream of IRE1 kinase as a key mediator of β cell death during UPR activation. In vivo JNK inhibition protected against β cell death in 2 distinct ER stress diabetes models. In human β cells, pharmacological inhibition of both JNK and p53 improved β cell survival during GRP78 knockdown–induced UPR. These findings provide insight into mechanisms causing β cell death during ER stress and outline possible therapeutic targets to preserve insulin secretory capacity in diabetes.

Authors

Rohit B. Sharma, Christine Darko, Ying Wang, Thalia A. Castro, Tara Doma Lama, Brian Gablaski, Andrew Rappa, David Redmond, Jason K. Kim, Amy S. Lee, Laura C. Alonso

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Figure 8

JNK inhibition decreases β cell death in Akita mice.

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JNK inhibition decreases β cell death in Akita mice. (A) Schematic of 5-...
(A) Schematic of 5-day in vivo treatment timeline and sample collection. (B) p-JNK staining intensity in insulin+ area of pancreas sections from Akita (Ak) mice with and without JNK inhibition; at least 8 islets were quantified from n = 3 mice in each group. (C) Random blood glucose at the beginning, day 3 and day 5 of treatment with either PBS or JNK inhibitor (n ≥ 15). (D–G) Pancreas sections (n ≥ 6) labeled for insulin (red), TUNEL (green), and DAPI (blue) were imaged (D) and quantified (E) for the percentage β cells that were TUNEL+. (F) β cell mass. (G) Plasma insulin levels at day 0 and day 5. (H) Schematic of 28-day in vivo treatment timeline. (I) Random blood glucose across the treatment period (n ≥ 11). (J) Plasma insulin levels (n ≥ 5). (K–M) Pancreas sections labeled for insulin (red), TUNEL (green) and DAPI (blue) were imaged (K) and quantified for the percentage β cells that were TUNEL+ (L) or for β cell mass (M). Males and females did not show marked differences for most outcomes and were combined for most panels. Scale bars: 50μm. Statistics by t test (B and J–M), 1-way ANOVA (E, F, I), or 2-way ANOVA (C and G). *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.