Nitric oxide produced in response to engagement of beta2 integrins on human neutrophils activates the monomeric GTPases Rap1 and Rap2 and promotes adhesion.
We found that engagement of beta2 integrins on human neutrophils increased the levels of GTP-bound Rap1 and Rap2. Also, the activation of Rap1 was blocked by PP1, SU6656, LY294002, GF109203X, or BAPTA-AM, which indicates that the downstream signaling events in Rap1 activation involve Src tyrosine kinases, phosphoinositide 3-kinase, protein kinase C, and release of calcium. Surprisingly, the beta2 integrin-induced activation of Rap2 was not regulated by any of the signaling pathways mentioned above. However, we identified nitric oxide as the signaling molecule involved in beta2 integrin-induced activation of Rap1 and Rap2. This was illustrated by the fact that engagement of beta2 integrins increased the production of nitrite, a stable end-product of nitric oxide. Furthermore, pretreatment of neutrophils with Nomega-monomethyl-L-arginine, or 1400W, which are inhibitors of inducible nitric-oxide synthase, blocked beta2 integrin-induced activation of Rap1 and Rap2. Similarly, Rp-8pCPT-cGMPS, an inhibitor of cGMP-dependent serine/threonine kinases, also blunted the beta2 integrin-induced activation of Rap GTPases. Also nitric oxide production and its downstream activation of cGMP-dependent serine/threonine kinases were essential for proper neutrophil adhesion by beta2 integrins. Thus, we made the novel findings that beta2 integrin engagement on human neutrophils triggers production of nitric oxide and its downstream signaling is essential for activation of Rap GTPases and neutrophil adhesion.
Jenei
Veronika
V
Department of Laboratory Medicine, Division of Experimental Pathology, Lund University, Malmö University Hospital, SE-20502 Malmö, Sweden.
Deevi
Ravi Kiran
RK
Adams
Catherine Anne
CA
Axelsson
Lena
L
Hirst
David Graham
DG
Andersson
Tommy
T
Dib
Karim
K
D018821:CD18 Antigens / Q000378:metabolism*; D020013:Calcium Signaling; D002448:Cell Adhesion / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D020668:rap GTP-Binding Proteins / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
D018821:CD18 Antigens; D047908:Intracellular Signaling Peptides and Proteins; C015482:protein kinase modulator; D009569:Nitric Oxide; D008345:Manganese; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; D011493:Protein Kinase C; C116756:RAP2A protein, human; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins