PKC-dependent phosphorylation of eNOS at T495 regulates eNOS coupling and endothelial barrier function in response to G+ -toxins

• Published in: PloS one 2014-07, Vol.9 (7), p.e99823
• Main Authors: Chen, Feng, Kumar, Sanjiv, Yu, Yanfang, Aggarwal, Saurabh, Gross, Christine, Wang, Yusi, Chakraborty, Trinad, Verin, Alexander D, Catravas, John D, Lucas, Rudolf, Black, Stephen M, Fulton, David J R
• Format: Article
• Language: English
• Subjects: Activation; Antibiotics; Bacterial Toxins - toxicity; Biology; Biology and life sciences; Calcium influx; Calcium ions; Caveolin 1 - metabolism; Caveolin-1; Cell permeability; Cholesterol; Cytolysins; Dissociation; Edema; Endothelial cells; Endothelial Cells - cytology; Endothelial Cells - drug effects; Endothelial Cells - metabolism; Gram-Positive Bacteria; HSP90 Heat-Shock Proteins - metabolism; Hsp90 protein; Humans; Kinases; Listeria; Lungs; Medicine and Health Sciences; Membrane permeability; Microvasculature; Mimicry; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type III - chemistry; Nitric Oxide Synthase Type III - metabolism; Nitric-oxide synthase; Permeability; Permeability - drug effects; Peroxynitrite; Phosphorylation; Phosphorylation - drug effects; Pneumolysin; Pneumonia; Pore formation; Pretreatment; Protein kinase C; Protein Kinase C-alpha - metabolism; Proteins; Pulmonary arteries; Rodents; Scaffolding; Signal Transduction - drug effects; Streptococcus infections; Substrate Specificity - drug effects; Superoxides - metabolism; Threonine; Toxins
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0099823

Gram positive (G+) infections make up ∼50% of all acute lung injury cases which are characterized by extensive permeability edema secondary to disruption of endothelial cell (EC) barrier integrity. A primary cause of increased permeability are cholesterol-dependent cytolysins (CDCs) of G+-bacteria, such as pneumolysin (PLY) and listeriolysin-O (LLO) which create plasma membrane pores, promoting Ca2+-influx and activation of PKCα. In human lung microvascular endothelial cells (HLMVEC), pretreatment with the nitric oxide synthase (NOS) inhibitor, ETU reduced the ability of LLO to increase microvascular cell permeability suggesting an endothelial nitric oxide synthase (eNOS)-dependent mechanism. LLO stimulated superoxide production from HLMVEC and this was prevented by silencing PKCα or NOS inhibition suggesting a link between these pathways. Both LLO and PLY stimulated eNOS T495 phosphorylation in a PKC-dependent manner. Expression of a phosphomimetic T495D eNOS (human isoform) resulted in increased superoxide and diminished nitric oxide (NO) production. Transduction of HLMVEC with an active form of PKCα resulted in the robust phosphorylation of T495 and increased peroxynitrite production, indicative of eNOS uncoupling. To determine the mechanisms underlying eNOS uncoupling, HLMVEC were stimulated with LLO and the amount of hsp90 and caveolin-1 bound to eNOS determined. LLO stimulated the dissociation of hsp90, and in particular, caveolin-1 from eNOS. Both hsp90 and caveolin-1 have been shown to influence eNOS uncoupling and a peptide mimicking the scaffolding domain of caveolin-1 blocked the ability of PKCα to stimulate eNOS-derived superoxide. Collectively, these results suggest that the G+ pore-forming toxins promote increased EC permeability via activation of PKCα, phosphorylation of eNOS-T495, loss of hsp90 and caveolin-1 binding which collectively promote eNOS uncoupling and the production of barrier disruptive superoxide.