Biology subjects

Brissova, M.

Publications and source records attributed to Brissova, M..

2 recordsLinked to original sources

bioRxiv2019

Human pseudoislet system enables detection of differences in G-protein-coupled-receptor signaling pathways between α and β cells

G-protein-coupled-receptors (GPCRs) modulate insulin secretion from {beta} cells and glucagon secretion from cells. Here, we developed an integrated approach to study the function of primary human islet cells using genetically modified pseudoislets that resemble native islets across multiple parameters. We studied the Gi and Gq GPCR pathways by expressing the designer receptors exclusively activated by designer drugs (DREADDs) hM4Di or hM3Dq. Activation of Gi signaling reduced insulin and glucagon secretion, while activation of Gq signaling stimulated glucagon secretion but had both stimulatory and inhibitory effects on insulin secretion. Further, we developed a microperifusion system that allowed synchronous acquisition of GCaMP6f biosensor signal and hormone secretory profiles and showed that the dual effects for Gq signaling occur through changes in intracellular Ca2+. By combining pseudoislets with a microfluidic system, we co-registered intracellular signaling dynamics and hormone secretion and demonstrated differences in GPCR signaling pathways between human {beta} and cells.

cell biology↗

bioRxiv2019

Myt Transcription Factors prevent stress-response gene over-activation to enable postnatal pancreatic β cell proliferation and function

Although stress response maintains cell function and survival under adverse conditions, over-activation of late-stage stress-gene effectors causes dysfunction and death. Here we show that the Myelin Transcription Factors (Myt 1, 2, and 3 TFs) prevent this over-activation. Co-inactivating Myt TFs in mouse pancreatic progenitors compromised postnatal {beta}-cell function, proliferation, and survival, preceded by upregulation of late-stage stress-response genes Activating Transcription Factors (e.g., Atf4) and Heat Shock Proteins (Hsps). Myt1 binds the putative enhancers of Atf4 and Hsps, whose over-expression in mouse {beta} cells largely recapitulated the Myt mutant phenotypes. Moreover, Myt(MYT)-TF levels were upregulated in functional mouse and human {beta} cells by metabolic stress but downregulated in those of type 2 diabetic islets that display ATF4 and HSP over-activation. Lastly, human MYT knockdown caused stress-gene over-activation and death in Endo-{beta}H1 cells. These findings suggest that the Myt TFs restrict stress-response to physiologically tolerable levels in mice and human.

developmental biology↗