Rapamycin protects against dominant negative-HNF1A-induced apoptosis in INS-1 cells

Abstract

HNF1A-maturity onset diabetes of the young (HNF1A-MODY) is caused by mutations in Hnf1a gene encoding the transcription factor hepatocyte nuclear factor 1alpha (HNF1A). An increased rate of apoptosis has been associated with the decrease in beta-cell mass that is a hallmark of HNF1A-MODY and other forms of diabetes. In a cellular model of HNF1A-MODY, we have recently shown that signalling through mammalian target of rapamycin (mTOR) is decreased by the overexpression of a dominant-negative mutant of HNF1A (DN-HNF1A). mTOR is a protein kinase which has important roles in cell metabolism and growth, but also in cell survival, where it has been shown to be both protective and detrimental. Here, we show that pharmacological inhibition of mTOR activity with rapamycin protected INS-1 cells against DN-HNF1A-induced apoptosis. Rapamycin also prevented DN-HNF1A-induced activation of AMP-activated protein kinase (AMPK), an intracellular energy sensor which we have previously shown to mediate DN-HNF1A-induced apoptosis. Conversely, activation of mTOR with leucine potentiated DN-HNF1A-induced apoptosis. Gene silencing of raptor (regulatory associated protein of mTOR), a subunit of mTOR complex 1 (mTORC1), also conferred protection on INS-1 cells against DN-HNF1A-induced apoptosis, confirming that mTORC1 mediates the protective effect. The potential relevance of this effect with regards to the clinical use of rapamycin as an immunosuppressant in diabetics post-transplantation is discussed.

Reciprocal regulation of mTOR complexes in pancreatic islets from humans with type 2 diabetes

“…Data show means ± SEM. § p = 0.05 compared with S6K1 inhibitor-treated basal (b); *p < 0.05 compared with untreated T2D islets (d) suppresses stress-induced apoptosis in beta cell lines [9,33] and improves beta cell function and thus corrects glucose homeostasis in the Akita mouse model of type 2 diabetes [34], chronic inhibition of mTORC1 by rapamycin causes glucose intolerance in mice [17,28]. This is due to the fact that chronic inhibition of mTORC1 with rapamycin disrupts mTORC2, which is crucial for the insulin-mediated suppression of hepatic gluconeogenesis [17] and for maintaining pancreatic functional beta cell mass [21].…”

Protective Role of p70S6K in Intestinal Ischemia/Reperfusion Injury in Mice

“…Although it has been well-established that the mTOR pathway plays a crucial role in cell function, its effects on different types of cells can vary. For instance, treatment of rapamycin induced cell apoptosis in a human gastric cancer cell line [26] and a non-small cell lung cancer cell line [27] , but caused cell resistance to apoptosis in rat beta cells [28] , rat renal tubular epithelial cells [29] , and human proximal tubular epithelial cells [30] . p70S6K-deficiency also protected against apoptosis in hepatocytes [31] .…”

Mechanisms by Which Metabolic Reprogramming in GSD1 Liver Generates a Favorable Tumorigenic Environment

“…100 Tumors bearing a HNF1A mutation have an increased proliferation rate due to the subsequent activation of the Phosphoinositide 3-kinase/AKT pathway. 101,102 The second group represents inflammatory HCAs. These HCAs are characterized by mutations that activate the IL-6 and JAK (Janus kinase)/STAT pathways and are the most prevalent HCAs, representing 50% of all HCAs.…”