Ezrin/radixin/moesin proteins are phosphorylated by TNF-alpha and modulate permeability increases in human pulmonary microvascular endothelial cells.
Endothelial cells (ECs) respond to TNF-alpha by altering their F-actin cytoskeleton and junctional permeability through mechanisms that include protein kinase C (PKC) and p38 MAPK. Ezrin, radixin, and moesin (ERM) regulate many cell processes that often require a conformational change of these proteins as a result of phosphorylation on a conserved threonine residue near the C terminus. This study tested the hypothesis that ERM proteins are phosphorylated on this critical threonine residue through TNF-alpha-induced activation of PKC and p38 and modulate permeability increases in pulmonary microvascular ECs. TNF-alpha induced ERM phosphorylation on the threonine residue that required activation of p38, PKC isoforms, and phosphatidylinositol-4-phosphate 5-kinase Ialpha, a major enzyme generating phosphatidylinositol 4,5-bisphosphate, and phosphorylated ERM were prominently localized at the EC periphery. TNF-alpha-induced ERM phosphorylation was accompanied by cytoskeletal changes, paracellular gap formation, and increased permeability to fluxes of dextran and albumin. These changes required activation of p38 and PKC and were completely prevented by inhibition of ERM protein expression using small interfering RNA. Thus, ERM proteins are phosphorylated through p38 and PKC-dependent mechanisms and modulate TNF-alpha-induced increases in endothelial permeability. Phosphorylation of ERM likely plays important roles in EC responses to TNF-alpha by modulating the F-actin cytoskeleton, adhesion molecules, and signaling events.
Koss
McKenzie
M
Division of Integrative Biology, Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106, USA.
Pfeiffer
Gordon R
GR
Wang
Ying
Y
Thomas
Sharon T
ST
Yerukhimovich
Michael
M
Gaarde
William A
WA
Doerschuk
Claire M
CM
Wang
Qin
Q
D001665:Binding Sites; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000098:blood supply*; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008833:Microcirculation / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D013912:Threonine / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099149:Ezrin
D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D011493:Protein Kinase C; D011994:Recombinant Proteins; D013912:Threonine; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099149:Ezrin; C071058:moesin; C071776:radixin