title: Regulation of the RhoA pathway in human endothelial cell spreading on type IV collagen: role of calcium influx.
abstract: We have shown that nonvoltage-operated Ca(2+) entry regulates human umbilical vein endothelial cell adhesion, migration, and proliferation on type IV collagen. We now demonstrate a requirement for Ca(2+) influx for activation of the RhoA pathway during endothelial cell spreading on type IV collagen. Reorganization of actin into stress fibers was complete when the cells where fully spread at 90 minutes. No actin organization into stress fibers was seen in endothelial cells plated on type I collagen, indicating a permissive effect of type IV collagen. CAI, a blocker of nonvoltage-operated Ca(2+) channels, prevented development of stress fiber formation in endothelial cells on type IV collagen. This permissive effect was augmented by Ca(2+) influx, as stimulated by 0. 5 microM thapsigargin or 0.1 microM ionomycin, yielding faster development of actin stress fibers. Ca(2+) influx and actin rearrangement in response to thapsigargin and ionomycin were abrogated by CAI. Activated, membrane-bound RhoA is a substrate for C3 exoenzyme which ADP-ribosylates and inactivates RhoA, preventing actin stress fiber formation. Pretreatment of endothelial cells with C3 exoenzyme prevented basal and thapsigargin-augmented stress fiber formation. While regulation of Ca(2+) influx did not alter RhoA translocation, it reduced in vitro ADP-ribosylation of RhoA (P(2)<0. 05), suggesting Ca(2+) influx is needed for RhoA activation during spreading on type IV collagen; no Ca(2+) regulated change in RhoA was seen in HUVECs spreading on type I collagen matrix. Blockade of Ca(2+) influx of HUVEC spread on type IV collagen also reduced tyrosine phosphorylation of p190Rho-GAP and blocked thapsigargin-enhanced binding of p190Rho-GAP to focal adhesion kinase. Thus, Ca(2+) influx is necessary for RhoA activation and for linkage of the RhoA/stress fiber cascade to the focal adhesion/focal adhesion kinase pathway during human umbilical vein endothelial cell spreading on type IV collagen.
authors.affiliation: Molecular Signaling Section, Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland 20892, USA.
authors.forename: L
authors.initials: L
authors.lastname: Masiero
authors.forename: K A
authors.initials: KA
authors.lastname: Lapidos
authors.forename: I
authors.initials: I
authors.lastname: Ambudkar
authors.forename: E C
authors.initials: EC
authors.lastname: Kohn
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000199:Actins / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001905:Botulinum Toxins; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000302:isolation & purification / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism / Q000494:pharmacology*; D003599:Cytoskeleton / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007700:Kinetics; D018919:Neovascularization, Physiologic / Q000502:physiology; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism; D011554:Pseudopodia / Q000502:physiology; D012097:Repressor Proteins; D013314:Stress, Mechanical; D019284:Thapsigargin / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D020742:rhoA GTP-Binding Protein / Q000032:analysis / Q000378:metabolism*
chemical_list: C074560:ARHGAP35 protein, human; D000199:Actins; D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D000246:Adenosine Diphosphate Ribose; D014443:Tyrosine; D019284:Thapsigargin; D003094:Collagen; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D001905:Botulinum Toxins; D020742:rhoA GTP-Binding Protein; D002118:Calcium