APPL1 prevents pancreatic beta cell death and inflammation by dampening NFκB activation in a mouse model of type 1 diabetes

The Journal of Gene Medicine

et al. 2019

Background: Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by the progressive destruction of insulin-production pancreatic β cells. Recently, microRNAs (miRNAs) have emerged as important regulators in T1D. The present study aimed to determine miR-885-3p expression in T1D patients and to examine the effects of miR-885-3p on the inflammatory response in human monocytes.Methods: Relevant gene expression levels were determined by a quantitative polymerase chain reaction; western blotting and enzyme-linked immunosorbent assays determined the respective protein levels; and the interaction between miRNA and the downstream targets was evaluated using a luciferase reporter assay.Results: MiR-885-3p is down-regulated and the levels of pro-inflammatory cytokines are increased in peripheral blood mononuclear cells (PBMCs) from T1D patients compared to healthy controls. MiR-885-3p overexpression suppressed mRNA expression and secreted protein levels of pro-inflammatory cytokines in THP-1. A luciferase reporter assay showed that miR-885-3p directly targeted the 3'untranslated region of Toll-like receptor 4 (TLR4) and miR-885-3p overexpression down-regulated TLR4 expression in THP-1 cells. The TLR4 mRNA expression level was increased in PBMCs isolated from T1D patients compared to heathy controls.TLR4 overexpression increased the secretion of pro-inflammatory cytokines and enhanced the activity of NF-κB signaling, and also attenuated the inhibitory effects of miR-885-3p overexpression on pro-inflammatory cytokine secretion and the activity of NF-κB signaling in THP-1 cells. Conclusions:The present study identified the down-regulation of miR-885-3p and up-regulation of TLR4 in PBMCs isolated from T1D patients. Further mechanistic data demonstrated that miR-885-3p overexpression represses the production of proinflammatory cytokines via targeting TLR4/NF-κB signaling in THP-1 cells.

Section: Discussionmentioning

confidence: 99%

Section: Tlr4 Was Directly Targeted By Mir-885-3pmentioning

confidence: 99%

MiR‐885‐3p is down‐regulated in peripheral blood mononuclear cells from T1D patients and regulates the inflammatory response via targeting TLR4/NF‐κB signaling

Zhang

The Journal of Gene Medicine

et al. 2019

“…The AAV vector plasmid was cotransfected with pAAV2 rep cap, and pAAV helper plasmids into HEK293 cells were obtained from American Type Culture Collection and free of mycoplasma contamination. AAVs (serotype 2) were purified by polyethylene glycol/aqueous two‐phase partitioning method and were titrated by qPCR analysis as we previously described .…”

Section: Methodsmentioning

confidence: 99%

“…APPL2 negatively controls insulin‐ or adiponectin‐stimulated glucose uptake in skeletal muscle , whereas APPL1 exerts opposite actions . In pancreatic β‐cells, APPL1 facilitates glucose‐stimulated insulin secretion by upregulating the expression of exocytotic machinery proteins via an Akt‐dependent pathway and protects against β‐cell apoptosis by inhibiting NF‐κB activation . Indeed, human subjects carrying loss‐of‐function mutation of APPL1 are diabetes and expression of APPL1 in human islets is positively correlated with glucose‐stimulated insulin secretion .…”

Section: Introductionmentioning

confidence: 99%

Activation of hypothalamic RIP ‐Cre neurons promotes beiging of WAT via sympathetic nervous system

et al. 2018

EMBO Reports

Self Cite

Activation of brown adipose tissue (BAT) and beige fat by cold increases energy expenditure. Although their activation is known to be differentially regulated in part by hypothalamus, the underlying neural pathways and populations remain poorly characterized. Here, we show that activation of rat-insulin-promoter-Cre (RIP-Cre) neurons in ventromedial hypothalamus (VMH) preferentially promotes recruitment of beige fat via a selective control of sympathetic nervous system (SNS) outflow to subcutaneous white adipose tissue (sWAT), but has no effect on BAT Genetic ablation of APPL2 in RIP-Cre neurons diminishes beiging in sWAT without affecting BAT, leading to cold intolerance and obesity in mice. Such defects are reversed by activation of RIP-Cre neurons, inactivation of VMH AMPK, or treatment with a β3-adrenergic receptor agonist. Hypothalamic APPL2 enhances neuronal activation in VMH RIP-Cre neurons and raphe pallidus, thereby eliciting SNS outflow to sWAT and subsequent beiging. These data suggest that beige fat can be selectively activated by VMH RIP-Cre neurons, in which the APPL2-AMPK signaling axis is crucial for this defending mechanism to cold and obesity.

“…loss-of-function APPL1 mutants are identified in the family with a high prevalence of diabetes, and APPL1 expression in the human pancreatic islet is positively correlated with GSIS (15). In addition, APPL1 protects pancreatic β-cells from apoptosis and inflammation in the type 1 diabetic mouse model by inhibiting nuclear factor NF-κB activation (16).…”

mentioning

confidence: 99%

The adaptor protein APPL2 controls glucose-stimulated insulin secretion via F-actin remodeling in pancreatic β-cells

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

Lin

et al. 2020

Self Cite

Filamentous actin (F-actin) cytoskeletal remodeling is critical for glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells, and its dysregulation causes type 2 diabetes. The adaptor protein APPL1 promotes first-phase GSIS by up-regulating soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein expression. However, whether APPL2 (a close homology of APPL1 with the same domain organization) plays a role in β-cell functions is unknown. Here, we show that APPL2 enhances GSIS by promoting F-actin remodeling via the small GTPase Rac1 in pancreatic β-cells. β-cell specific abrogation of APPL2 impaired GSIS, leading to glucose intolerance in mice. APPL2 deficiency largely abolished glucose-induced first- and second-phase insulin secretion in pancreatic islets. Real-time live-cell imaging and phalloidin staining revealed that APPL2 deficiency abolished glucose-induced F-actin depolymerization in pancreatic islets. Likewise, knockdown of APPL2 expression impaired glucose-stimulated F-actin depolymerization and subsequent insulin secretion in INS-1E cells, which were attributable to the impairment of Ras-related C3 botulinum toxin substrate 1 (Rac1) activation. Treatment with the F-actin depolymerization chemical compounds or overexpression of gelsolin (a F-actin remodeling protein) rescued APPL2 deficiency-induced defective GSIS. In addition, APPL2 interacted with Rac GTPase activating protein 1 (RacGAP1) in a glucose-dependent manner via the bin/amphiphysin/rvs-pleckstrin homology (BAR-PH) domain of APPL2 in INS-1E cells and HEK293 cells. Concomitant knockdown of RacGAP1 expression reverted APPL2 deficiency-induced defective GSIS, F-actin remodeling, and Rac1 activation in INS-1E cells. Our data indicate that APPL2 interacts with RacGAP1 and suppresses its negative action on Rac1 activity and F-actin depolymerization thereby enhancing GSIS in pancreatic β-cells.