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Insulin demand regulates ? cell number via the unfolded protein response.

ABSTRACT: Although stem cell populations mediate regeneration of rapid turnover tissues, such as skin, blood, and gut, a stem cell reservoir has not been identified for some slower turnover tissues, such as the pancreatic islet. Despite lacking identifiable stem cells, murine pancreatic ? cell number expands in response to an increase in insulin demand. Lineage tracing shows that new ? cells are generated from proliferation of mature, differentiated ? cells; however, the mechanism by which these mature cells sense systemic insulin demand and initiate a proliferative response remains unknown. Here, we identified the ? cell unfolded protein response (UPR), which senses insulin production, as a regulator of ? cell proliferation. Using genetic and physiologic models, we determined that among the population of ? cells, those with an active UPR are more likely to proliferate. Moreover, subthreshold endoplasmic reticulum stress (ER stress) drove insulin demand-induced ? cell proliferation, through activation of ATF6. We also confirmed that the UPR regulates proliferation of human ? cells, suggesting that therapeutic UPR modulation has potential to expand ? cell mass in people at risk for diabetes. Together, this work defines a stem cell-independent model of tissue homeostasis, in which differentiated secretory cells use the UPR sensor to adapt organ size to meet demand.

SUBMITTER: Sharma RB

PROVIDER: S-EPMC4607122 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Insulin demand regulates β cell number via the unfolded protein response.

Sharma Rohit B RB O'Donnell Amy C AC Stamateris Rachel E RE Ha Binh B McCloskey Karen M KM Reynolds Paul R PR Arvan Peter P Alonso Laura C LC

The Journal of clinical investigation 20150921 10

Although stem cell populations mediate regeneration of rapid turnover tissues, such as skin, blood, and gut, a stem cell reservoir has not been identified for some slower turnover tissues, such as the pancreatic islet. Despite lacking identifiable stem cells, murine pancreatic β cell number expands in response to an increase in insulin demand. Lineage tracing shows that new β cells are generated from proliferation of mature, differentiated β cells; however, the mechanism by which these mature ce ...[more]

PMID: 26389675

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Project description:Campylobacter jejuni is a major cause of bacterial foodborne illness in humans worldwide. Bacterial entry into a host eukaryotic cell involves the initial steps of adherence and invasion, which generally activate several cell-signaling pathways that induce the activation of innate defense systems, which leads to the release of proinflammatory cytokines and induction of apoptosis. Recent studies have reported that the unfolded protein response (UPR), a system to clear unfolded proteins from the endoplasmic reticulum (ER), also participates in the activation of cellular defense mechanisms in response to bacterial infection. However, no study has yet investigated the role of UPR in C. jejuni infection. Hence, the aim of this study was to deduce the role of UPR signaling via induction of ER stress in the process of C. jejuni infection. The results suggest that C. jejuni infection suppresses global protein translation. Also, 12 h of C. jejuni infection induced activation of the eIF2? pathway and expression of the transcription factor CHOP. Interestingly, bacterial invasion was facilitated by knockdown of UPR-associated signaling factors and treatment with the ER stress inducers, thapsigargin and tunicamycin, decreased the invasive ability of C. jejuni. An investigation into the mechanism of UPR-mediated inhibition of C. jejuni invasion showed that UPR signaling did not affect bacterial adhesion to or survival in the host cells. Further, Salmonella Enteritidis or FITC-dextran intake were not regulated by UPR signaling. These results indicated that the effect of UPR on intracellular intake was specifically found in C. jejuni infection. These findings are the first to describe the role of UPR in C. jejuni infection and revealed the participation of a new signaling pathway in C. jejuni invasion. UPR signaling is involved in defense against the early step of C. jejuni invasion and thus presents a potential therapeutic target for the treatment of C. jejuni infection.

Dataset Information

Insulin demand regulates ? cell number via the unfolded protein response.

Publications

Insulin demand regulates β cell number via the unfolded protein response.

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