Interleukin-1 beta induces posttranslational carboxymethylation and alterations in subnuclear distribution of lamin B in insulin-secreting RINm5F cells.
We examined the effects of interleukin-1beta (IL-1beta) treatment on the distribution and degradation of lamin B in the nuclear fraction from insulin-secreting RINm5F cells. Western blot analysis indicated that IL-1beta treatment caused significant alterations in the redistribution of lamin B, specifically between the Triton X-100-soluble (membrane) and -insoluble (matrix) fractions of the nucleus. IL-1beta treatment also increased the lamin carboxymethyltransferase activity and the relative abundance of the carboxymethylated lamin in the nuclear fraction. A significant increase in the relative abundance of lamin B degradation products was also observed in the nuclear fraction from the IL-1beta-treated cells. These findings are compatible with a measurable increase in the lamin-degrading caspase-6 activity in IL-1beta-treated cells. Confocal microscopic observation of IL-1beta-treated cells suggested a significant dissociation of lamin B from the nuclear lamina and its subsequent association with the DNA-rich elements within the nucleus. N(G)-monomethyl-l-arginine, a known inhibitor of inducible nitric oxide synthetase (iNOS), markedly inhibited IL-1beta-induced iNOS gene expression, NO release, caspase-3 and caspase-6 activation, lamin B degradation, and loss of metabolic cell viability, indicating that the observed IL-1beta-induced effects on nuclear lamin B involve the intermediacy of NO. Together, our data support the hypothesis that IL-1beta treatment results in significant increase in the carboxymethylation of lamin B, which would place lamin B in a strategic location for its degradation mediated by caspases. This could possibly lead to dissolution of the nuclear envelope, culminating in the demise of the effete beta-cell.
Veluthakal
Rajakrishnan
R
Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, 259 Mack Ave., Detroit, MI 48201, USA.
Amin
Rajesh
R
Kowluru
Anjaneyulu
A
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007375:Interleukin-1 / Q000494:pharmacology*; D034921:Lamin Type B / Q000187:drug effects / Q000378:metabolism*; D018613:Microscopy, Confocal; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009685:Nuclear Envelope / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional; D051381:Rats
D004791:Enzyme Inhibitors; D007328:Insulin; D007375:Interleukin-1; D034921:Lamin Type B; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D020169:Caspases