Transgenic mice expressing Shb adaptor protein under the control of rat insulin promoter exhibit altered viability of pancreatic islet cells

Mol Med. 1999 Mar;5(3):169-80.

Abstract

Background: The Src-homology 2 domain-containing adaptor protein Shb was recently cloned as a serum-inducible gene in the insulin-producing beta-TC1 cell line. Subsequent studies have revealed an involvement of Shb for apoptosis in NIH3T3 fibroblasts and differentiation in the neuronal PC12 cells. To assess a role of Shb for beta-cell function, transgenic mice utilizing the rat insulin promoter to drive expression of Shb were generated.

Materials and methods: A gene construct allowing the Shb cDNA to be expressed from the rat insulin 2 promoter was microinjected into fertilized mouse oocytes and implanted into pseudopregnant mice. Mice containing a low copy number of this transgene were bred and used for further experimentation. Shb expression was determined by Western blot analysis. The insulin-positive area of whole pancreas, insulin secretion of isolated islets and islet cell apoptosis, glucose tolerance tests, and in vivo sensitivity to multiple injections of the beta-cell toxin streptozotocin were determined in control CBA and Shb-transgenic mice.

Results: Western blot analysis revealed elevated islet content of the Shb protein. Shb-transgenic mice displayed enhanced glucose-disappearance rates in response to an intravenous glucose injection. The relative pancreatic beta-cell area neonatally and at 6 months of age were increased in the Shb-transgenic mice. Islets isolated from Shb-transgenic mice showed enhanced insulin secretion in response to glucose and increased insulin and DNA content. Apoptosis was increased in islets isolated from Shb-transgenic mice compared with control islets both under basal conditions and after incubation with IL-1 beta + IFN-gamma. Rat insulinoma RINm5F cells overexpressing Shb displayed decreased viability during culture in 0.1% serum and after exposure to a cytotoxic dose of nicotinamide. Shb-transgenic mice injected with multiple doses of streptozotocin showed increased blood glucose values compared with the corresponding controls, suggesting increased in vivo susceptibility to this toxin.

Conclusion: The results suggest that Shb has dual effects on beta-cell growth: whereas Shb increases beta-cell formation during late embryonal stages, Shb also enhances beta-cell death under certain stressful conditions and may thus contribute to beta-cell destruction in type 1 diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Blood Glucose / metabolism*
  • Cell Division
  • Cell Survival
  • Diabetes Mellitus, Experimental / chemically induced
  • Diabetes Mellitus, Experimental / metabolism
  • Diabetes Mellitus, Experimental / pathology
  • Female
  • Glucose / pharmacology
  • Homeostasis
  • Insulin / genetics*
  • Insulin / metabolism
  • Insulin Secretion
  • Interferon-gamma / pharmacology
  • Interleukin-1 / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / physiology*
  • Male
  • Mice
  • Mice, Inbred CBA
  • Mice, Transgenic
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism
  • Rats
  • Streptozocin

Substances

  • Blood Glucose
  • Insulin
  • Interleukin-1
  • Proto-Oncogene Proteins
  • Shb protein, mouse
  • Shb protein, rat
  • Streptozocin
  • Interferon-gamma
  • Glucose