G protein?coupled receptor signaling is required for the navigation of immune cells along chemoattractant gradients. However, chemoattractant receptors may couple to more than one type of heterotrimeric G protein, each of which consists of a G?, G?, and G? subunit, making it difficult to delineate the critical signaling pathways. Here, we used knockout mouse models and time-lapse microscopy to elucidate G? and G? subunits contributing to complement C5a receptor-mediated chemotaxis. Complement C5a-mediated chemokinesis and chemotaxis were almost completely abolished in macrophages lacking Gnai2 (encoding G?(i2)), consistent with a reduced leukocyte recruitment previously observed in Gnai2(?/?) mice, whereas cells lacking Gnai3 (G?(i3)) exhibited only a slight decrease in cell velocity. Surprisingly, C5a-induced Ca2+ transients and lamellipodial membrane spreading were persistent in Gnai2(?/?) macrophages. Macrophages lacking both Gnaq (G?(q)) and Gna11 (G?(11)) or both Gna12 (G?(12)) and Gna13 (G?(13)) had essentially normal chemotaxis, Ca2+ signaling, and cell spreading, except Gna12/Gna13-deficient macrophages had increased cell velocity and elongated trailing ends. Moreover, Gnaq/Gna11-deficient cells did not respond to purinergic receptor P2Y(2) stimulation. Genetic deletion of Gna15 (G?(15)) virtually abolished C5a-induced Ca2+ transients, but chemotaxis and cell spreading were preserved. Homozygous Gnb1 (G?(1)) deletion was lethal, but mice lacking Gnb2 (G?(2)) were viable. Gnb2(?/?) macrophages exhibited robust Ca2+ transients and cell spreading, albeit decreased cell velocity and impaired chemotaxis. In summary, complement C5a-mediated chemotaxis requires G?(i2) and G?(2), but not Ca2+ signaling, and membrane protrusive activity is promoted by G proteins that deplete phosphatidylinositol 4,5-bisphosphate.
|Titolo:||Knockout mouse models reveal the contributions of G protein subunits to complement C5a receptor-mediated chemotaxis|
|Data di pubblicazione:||2020|
|Appare nelle tipologie:||01.01 Articolo in Rivista|