Signals for actin polymerization in neutrophils.
The role of the G proteins and of changes in the cytoplasmic levels of calcium and hydrogen ions in the initiation of actin polymerization in the neutrophils are discussed. The presently available data allow us to draw the following conclusions: 1) G proteins play a mediatory role in the transmission of the signal(s) generated upon receptor occupancy that leads to the observed cytoskeletal changes. 2) Increases in cytoplasmic free calcium appear to be neither necessary nor sufficient for the initiation of actin polymerization. 3) The activation of the Na+/H+ antiport is unrelated to the initiation of actin polymerization. 4) A possible relationship holds between the chemotactic factor elicited cytoplasmic acidification and the initiation of the reorganization of the cytoskeletal structures of these cells. However, further studies are necessary in order to further examine this hypothesis. Several avenues of research still need to be explored in order to derive a more comprehensive understanding of the mechanisms regulating the dynamic nature of the cytoskeleton of the neutrophils. These include, among others, potential roles of the hydrolysis of the polyphosphoinositides, and of the surface glycoproteins in this process.
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002630:Chemotactic Factors / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009504:Neutrophils / Q000378:metabolism*; D011108:Polymers
D000199:Actins; D002630:Chemotactic Factors; D011108:Polymers; D019204:GTP-Binding Proteins; D002118:Calcium