Multiple signal messengers generated by terminal complement complexes and their role in terminal complement complex elimination.
The best established function of C5b-9 is the ability to lyse or kill cells after assembly in the plasma membrane. In addition to this cytolytic function, increasing evidence suggests that C5b-9 also stimulate a variety of cell functions in vitro. Relatively little is known about the C5b-9 signals responsible for cell activation other than a transient increase in cytosolic Ca2+ primarily due to Ca2+ influx that have been determined in a cell population. In this report, signal messenger generation in Ehrlich cells by the sublytic terminal complement complexes (TCC), C5b-9, C5b-8, and C5b-7, was further examined, as well as the role of signal messengers in stimulating elimination of TCC from the cell surface. Changes in cytosolic Ca2+ were monitored in individual cells after a single dose of C5b-9 by digital imaging fluorescence microscopy that revealed oscillations in cytosolic Ca2+ over a period of 10 min. Sublytic C5b-9 substantially increased protein kinase C (PKC) activity at an external Ca2+ concentration of 1.5 mM. C5b-9-mediated PKC activation could be inhibited by 60 to 80% when external Ca2+ was reduced to 0.015 mM. C5b-8, but not C5b-7, activated PKC to a lesser extent. C5b-8 and C5b-7 also stimulated an increase in cAMP. Rapid elimination of TCC known to be stimulated by Ca2+ signal was partially inhibited by protein kinase inhibitors, H-7 and to a lesser extent by HA1004, suggesting a role for PKC in the elimination response. TCC elimination was not accelerated by agents that increase cAMP.
Carney
D F
DF
Department of Pathology, University of Maryland School of Medicine, Baltimore 21201.
Lang
T J
TJ
Shin
M L
ML
D002118:Calcium / Q000502:physiology; D002451:Cell Compartmentation; D003182:Complement C5; D015938:Complement Membrane Attack Complex / Q000502:physiology*; D003165:Complement System Proteins / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D003182:Complement C5; D015938:Complement Membrane Attack Complex; C042295:complement C5b-8 complex; D015759:Ionomycin; C037453:complement C5b-7 complex; D003165:Complement System Proteins; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium