<i>Grp78</i> Heterozygosity Promotes Adaptive Unfolded Protein Response and Attenuates Diet-Induced Obesity and Insulin Resistance

Maganty

Journal of Cell Science

et al. 2012

SummaryER stress leads to upregulation of multiple folding and quality control components, known as the unfolded protein response (UPR). Glucose Regulated Protein 78 (GRP78) (also known as binding immunoglobulin protein, BiP, and HSPA5) and GRP94 are often upregulated coordinately as part of this homeostatic response. Given that endoplasmic reticulum (ER) chaperones have distinct sets of clients, we asked how cells respond to ablation of individual chaperones. The cellular responses to silencing BiP, GRP94, HSP47, PDIA6 and OS-9, were distinct. When BiP was silenced, a widespread UPR was observed, but when GRP94 was either inhibited or depleted by RNA interference (RNAi), the expression of only some genes was induced, notably those encoding BiP and protein disulfide isomerase A6 (PDIA6). Silencing of HSP47 or OS-9 did not lead to any compensatory induction of other genes. The selective response to GRP94 depletion was distinct from a typical ER stress response, both because other UPR target genes were not affected and because the canonical UPR signaling branches were not activated. The response to silencing of GRP94 did not preclude further UPR induction when chemical stress was imposed. Importantly, re-expression of wild-type GRP94 in the silenced cells prevented the upregulation of BiP and PDIA6, whereas re-expression of an ATPase-deficient GRP94 mutant did not, indicating that cells monitor the activity state of GRP94. These findings suggest that cells are able to distinguish among folding resources and generate distinct responses.

Section: Resultsmentioning

confidence: 78%

Limitation of individual folding resources in the ER leads to outcomes distinct from the unfolded protein response

Maganty

Journal of Cell Science

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

“…S2A). In contrast to other tissues where GRP94 was up-regulated to compensate for GRP78 haploinsufficiency (29), the level of GRP94 in the ductal structures was similar in the PKC and PKC78 f/+ mice (Fig. S2A).…”

Section: Resultsmentioning

confidence: 82%

GRP78 haploinsufficiency suppresses acinar-to-ductal metaplasia, signaling, and mutant Kras -driven pancreatic tumorigenesis in mice

Shen

Zhu

et al. 2017

Self Cite

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal disease in critical need of new therapeutic strategies. Here, we report that the stress-inducible 78-kDa glucose-regulated protein (GRP78/HSPA5), a key regulator of endoplasmic reticulum homeostasis and PI3K/AKT signaling, is overexpressed in the acini and PDAC of Pdx1-Cre;Kras G12D/+ ;p53 f/+ (PKC) mice as early as 2 mo, suggesting that GRP78 could exert a protective effect on acinar cells under stress, as during PDAC development. The PKC pancreata bearing wild-type Grp78 showed detectable PDAC by 3 mo and rapid subsequent tumor growth. In contrast, the PKC pancreata bearing a Grp78 f/+ allele (PKC78 f/+ mice) expressing about 50% of GRP78 maintained normal sizes during the early months, with reduced proliferation and suppression of AKT, S6, ERK, and STAT3 activation. Acinar-to-ductal metaplasia (ADM) has been identified as a key tumor initiation mechanism of PDAC. Compared with PKC, the PKC78 f/+ pancreata showed substantial reduction of ADM as well as pancreatic intraepithelial neoplasia-1 (PanIN-1), PanIN-2, and PanIN-3 and delayed onset of PDAC. ADM in response to transforming growth factor α was also suppressed in ex vivo cultures of acinar cell clusters isolated from mouse pancreas bearing targeted heterozygous knockout of Grp78 (c78 f/+ ) and subjected to 3D culture in collagen. We further discovered that GRP78 haploinsufficiency in both the PKC78 f/+ and c78 f/+ pancreata leads to reduction of epidermal growth factor receptor, which is critical for ADM initiation. Collectively, our studies establish a role for GRP78 in ADM and PDAC development.glucose-regulated protein 78 | GRP78 | pancreatic ductal adenocarcinoma | acinar-to-ductal metaplasia | Kras P ancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest diseases with limited therapeutic options and an overall 5-y survival rate of <10%; therefore, identification of targetable key players in tumor initiation as well as tumor maintenance is urgently needed (1). PDAC is believed to arise from a range of preneoplastic mucinous lesions with ductal morphology, pancreatic intraepithelial neoplasia (PanIN) being the most common in humans (2). About 90% of PDAC contains activating mutations of KRAS whereas 50-75% contain mutations in Tp53 (1). Mutationally activated oncogenic KRAS signals through the PI3K-PDK1-AKT pathway and the canonical mitogen-activated protein kinase pathway via RAF-MEK1/2-ERK1/2, as well as via positive feedback activation of receptor tyrosine kinases engaged by autocrine and paracrine stimuli (3). Although the histological appearance of PDAC suggests a ductal cell of origin, accumulating evidence reveals that PDAC originates primarily through transdifferentiation of acinar cells into ductal cells in a process referred to as acinar-to-ductal metaplasia (ADM), although centroacinar cells and pancreas precursor cells could also give rise to PDAC (2, 4, 5). To study PDAC, a pancreatic cancer mouse model mimicking human PDAC has been established using the pancreatic...

“…A recent study showed that arctigenin served as an anti-tumour agent by blocking the expression of unfolded protein response (UPR) target genes [25]. Although UPR has been reported to be involved in the pathophysiology of insulin resistance and diabetes [26][27][28], our preliminary work showed that arctigenin had no effects on UPR or the Jun N-terminal kinase (JNK) pathway in liver of ob/ob mice (ESM Fig. 2).…”

Section: Discussionmentioning

confidence: 77%

Arctigenin, a natural compound, activates AMP-activated protein kinase via inhibition of mitochondria complex I and ameliorates metabolic disorders in ob/ob mice

Huang

Gong

et al. 2011

Diabetologia

Aims/hypothesis Arctigenin is a natural compound that had never been previously demonstrated to have a glucoselowering effect. Here it was found to activate AMPactivated protein kinase (AMPK), and the mechanism by which this occurred, as well as the effects on glucose and lipid metabolism were investigated. Methods 2-Deoxyglucose uptake and AMPK phosphorylation were examined in L6 myotubes and isolated skeletal muscle. Gluconeogenesis and lipid synthesis were evaluated in rat primary hepatocytes. The acute and chronic effects of arctigenin on metabolic abnormalities were observed in C57BL/6J and ob/ob mice. Changes in mitochondrial membrane potential were measured using the J-aggregate-forming dye, JC-1. Analysis of respiration of L6 myotubes or isolated mitochondria was conducted in a channel oxygen system. Results Arctigenin increased AMPK phosphorylation and stimulated glucose uptake in L6 myotubes and isolated skeletal muscles. In primary hepatocytes, it decreased gluconeogenesis and lipid synthesis. The enhancement of glucose uptake and suppression of hepatic gluconeogenesis and lipid synthesis by arctigenin were prevented by blockade of AMPK activation. The respiration of L6 myotubes or isolated mitochondria was inhibited by arctigenin with a specific effect on respiratory complex I. A single oral dose of arctigenin reduced gluconeogenesis in C57BL/6J mice. Chronic oral administration of arctigenin lowered blood glucose and improved lipid metabolism in ob/ob mice. Conclusions/interpretation This study demonstrates a new role for arctigenin as a potent indirect activator of AMPK via inhibition of respiratory complex I, with beneficial effects on metabolic disorders in ob/ob mice. This highlights the potential value of arctigenin as a possible treatment of type 2 diabetes.