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

Diabetologia. 2017 Mar;60(3):464-474. doi: 10.1007/s00125-016-4185-z. Epub 2016 Dec 23.


Aims/hypothesis: Beta cell inflammation and demise is a feature of type 1 diabetes. The insulin-sensitising molecule 'adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1' (APPL1), which contains an NH2-terminal Bin/Amphiphysin/Rvs domain, a central pleckstrin homology domain and a COOH-terminal phosphotyrosine-binding domain, has been shown to modulate inflammatory response in various cell types but its role in regulating beta cell mass and inflammation in type 1 diabetes remains unknown. Thus, we investigated whether APPL1 prevents beta cell apoptosis and inflammation in diabetes.

Methods: Appl1-knockout mice and their wild-type littermates, as well as C57BL/6N mice injected with adeno-associated virus encoding APPL1 or green fluorescent protein, were treated with multiple-low-dose streptozotocin (MLDS) to induce experimental type 1 diabetes. Their glucose metabolism and beta cell function were assessed. The effect of APPL1 deficiency on beta cell function upon exposure to a diabetogenic cytokine cocktail (CKS; consisting of TNF-α, IL-1β and IFN-γ) was assessed ex vivo.

Results: Expression of APPL1 was significantly reduced in pancreatic islets from mouse models of type 1 diabetes or islets treated with CKS. Hyperglycaemia, beta cell loss and insulitis induced by MLDS were exacerbated by genetic deletion of Appl1 but were alleviated by beta cell-specific overexpression of APPL1. APPL1 preserved beta cell mass by reducing beta cell apoptosis upon treatment with MLDS. Mechanistically, APPL1 deficiency potentiate CKS-induced phosphorylation of NFκB inhibitor, α (IκBα) and subsequent phosphorylation and transcriptional activation of p65, leading to a dramatic induction of NFκB-regulated apoptotic and proinflammatory programs in beta cells. Pharmacological inhibition of NFκB or inducible NO synthase (iNOS) largely abrogate the detrimental effects of APPL1 deficiency on beta cell functions.

Conclusions/interpretation: APPL1 negatively regulates inflammation and apoptosis in pancreatic beta cells by dampening the NFκB-iNOS-NO axis, representing a promising target for treating type 1 diabetes.

Keywords: APPL1; Beta cell apoptosis; Beta cell inflammation; NFκB; Streptozotocin; Type 1 diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / deficiency
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Apoptosis / genetics
  • Apoptosis / physiology
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Cell Line
  • Chemokine CCL2 / genetics
  • Chemokine CCL2 / metabolism
  • Diabetes Mellitus, Type 1 / genetics
  • Diabetes Mellitus, Type 1 / metabolism*
  • HEK293 Cells
  • Humans
  • Immunohistochemistry
  • Inflammation / genetics
  • Inflammation / metabolism*
  • Insulin-Secreting Cells / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NF-kappa B / metabolism*
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / metabolism
  • Nitrogen Oxides / metabolism
  • Pancreas / metabolism
  • Rats
  • Real-Time Polymerase Chain Reaction
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Streptozocin / toxicity


  • Adaptor Proteins, Signal Transducing
  • Appl1 protein, mouse
  • Chemokine CCL2
  • NF-kappa B
  • Nitrogen Oxides
  • Streptozocin
  • Nitric Oxide Synthase Type II
  • Caspase 3