| 1. |
- Ydrenius, Liselotte, et al.
(författare)
-
Activation of cAMP-dependent protein kinase is necessary for actin rearrangements in human neutrophils during phagocytosis
- 2000
-
Ingår i: Journal of Leukocyte Biology. - 0741-5400 .- 1938-3673. ; 67:4, s. 520-528
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the role of cAMP and cAMP-dependent protein kinase (cAPK) in neutrophil phagocytosis. Inhibition of cAPK with H-89 reduced complement- and IgG-dependent phagocytosis to 83 and 46%, respectively. Fluorescence intensity measurements of phalloidin-stained actin in neutrophils showed a reduced amount of filamentous actin (F-actin) in pseudopods and around the phagosome in cells treated with H-89 or cAMP-elevating agents (forskolin and rolipram). The amount of phosphotyrosine-containing proteins was also reduced in pseudopods and around the phagosome. Taken together, the data show that cAMP/cAPK regulates F-actin reorganization during receptor-mediated phagocytosis, particularly triggered by IgG-FcR interaction. Our results support the hypothesis that active subcortical reorganization of F-actin is a prerequisite for FcR-mediated phagocytosis, but is less important during CR3-mediated ingestion.
|
|
| 2. |
- Forsberg, Maria, 1973-, et al.
(författare)
-
Activation of Rac2 and Cdc42 on Fc and complement receptor ligation in human neutrophils
- 2003
-
Ingår i: Journal of Leukocyte Biology. - : Oxford University Press (OUP). - 0741-5400 .- 1938-3673. ; 74:4, s. 611-619
-
Tidskriftsartikel (refereegranskat)abstract
- Phagocytosis is a complex process engaging a concerted action of signal-transduction cascades that leads to ingestion, subsequent phagolysosome fusion, and oxidative activation. We have previously shown that in human neutrophils, C3bi-mediated phagocytosis elicits a significant oxidative response, suggesting that activation of the small GTPase Rac is involved in this process. This is contradictory to macrophages, where only Fc receptor for immunoglobulin G (FcγR)-mediated activation is Rac-dependent. The present study shows that engagement of the complement receptor 3 (CR3) and FcγR and CR3- and FcγR-mediated phagocytosis activates Rac, as well as Cdc42. Furthermore, following receptor-engagement of the CR3 or FcγRs, a downstream target of these small GTPases, p21-activated kinase, becomes phosphorylated, and Rac2 is translocated to the membrane fraction. Using the methyltransferase inhibitors N-acetyl-S-farnesyl-L-cysteine and N-acetyl-S-geranylgeranyl-L-cysteine, we found that the phagocytic uptake of bacteria was not Rac2- or Cdc42-dependent, whereas the oxidative activation was decreased. In conclusion, our results indicate that in neutrophils, Rac2 and Cdc42 are involved in FcR- and CR3-induced activation and for properly functioning signal transduction involved in the generation of oxygen radicals.
|
|
