Phosphorylation of caveolin-1 on tyrosine-14 induced by ROS enhances palmitate-induced death of beta-pancreatic cells

Abstract

A considerable body of evidence exists implicating high levels of free saturated fatty acids in beta pancreatic cell death, although the molecular mechanisms and the signaling pathways involved have not been clearly defined. The membrane protein caveolin-1 has long been implicated in cell death, either by sensitizing to or directly inducing apoptosis and it is normally expressed in beta cells. Here, we tested whether the presence of caveolin-1 modulates free fatty acid-induced beta cell death by reexpressing this protein in MIN6 murine beta cells lacking caveolin-1. Incubation of MIN6 with palmitate, but not oleate, induced apoptotic cell death that was enhanced by the presence of caveolin-1. Moreover, palmitate induced de novo ceramide synthesis, loss of mitochondrial transmembrane potential and reactive oxygen species (ROS) formation in MIN6 cells. ROS generation promoted caveolin-1 phosphorylation on tyrosine-14 that was abrogated by the anti-oxidant N-acetylcysteine or the incubation with the Src-family kinase inhibitor, PP2 (4-amino-5-(4-chlorophenyl)-7(dimethylethyl)pyrazolo[3,4-d]pyrimidine). The expression of a non-phosphorylatable caveolin-1 tyrosine-14 to phenylalanine mutant failed to enhance palmitate-induced apoptosis while for MIN6 cells expressing the phospho-mimetic tyrosine-14 to glutamic acid mutant caveolin-1 palmitate sensitivity was comparable to that observed for MIN6 cells expressing wild type caveolin-1. Thus, caveolin-1 expression promotes palmitate-induced ROS-dependent apoptosis in MIN6 cells in a manner requiring Src family kinase mediated tyrosine-14 phosphorylation.

Presence of Androgen Receptor Variant in Neuronal Lipid Rafts

“…Posttranslational modifications (e.g., palmitoylation and phosphorylation) commonly occur in caveolin proteins and steroid receptors ( Parat and Fox, 2001 ; Fukata and Fukata, 2010 ; Kim et al, 2011 ). A common initiator of posttranslational modifications in caveolin includes oxidative stress ( Kim et al, 2000 ; Volonté et al, 2001 ; Wehinger et al, 2015 ), and testosterone can act as an oxidative stressor ( Holmes et al, 2013, 2016 ). Therefore, it is possible that testosterone, via oxidative stress, is increasing posttranslational modifications in caveolin protein, resulting in the caveolin/AR45 complex shifting to higher-density protein fractions.…”

Oxidative stress and calcium dysregulation by palmitate in type 2 diabetes

“…32 However, the overproduction of ROS in pathologic conditions has detrimental consequences, causing organellar stress, injury and cell death. 33, 34 Palmitate is a potent inducer of ROS in a number of cell types, including pancreatic β cells, 35, 36, 37 cardiomyocytes, 34, 38 vascular smooth muscle cells, 39 endothelial cells, 40 skeletal muscle cells, 41 glomerular podocytes, 30 hepatocytes 42 and adipocytes. 43 CD36 appears to be required for fatty acid-induced ROS production due to the fact that the knockdown of CD36 prevents palmitate-dependent oxidative stress.…”

Caveolin-1 in the regulation of cell metabolism: a cancer perspective

“…Accordingly, DHA treatment caused cholesterol-dependent co-localisation of CAV1 and epidermal growth factor receptor (EGFR) with lysosome associated membrane protein 1 (LAMP-1), with an onward down-regulation of lipid-raft associated onco-proteins, including EGFR, HSP90, AKT and SRC [86]. Furthermore, expression of tyrosine-14 phosphorylated CAV1 accelerated palmitate-induced apoptotic cell death in pancreatic beta cells [87]. Taken together, these studies reveal that CAV1 is associated with fatty acid metabolism, offering insights for onward investigation in cancer.…”