Opposite effects of rho family GTPases on engulfment of apoptotic cells by macrophages.
The efficient engulfment of apoptotic cells by professional or nonprofessional phagocytes is critical to maintain mammalian homeostasis. To identify molecules involved in the engulfment of apoptotic cells, we established a retrovirus-based expression cloning system coupled with the engulfment assay. By screening a cDNA library of a mouse macrophage cell line, we identified two small GTPase family members (RhoG and Rab5) that enhanced the engulfment of apoptotic cells. By examining other small GTPase family members, we found that Rac1 enhanced the engulfment of apoptotic cells, whereas RhoA inhibited the process. Accordingly, the expression of a dominant-negative form of RhoG or Rac1 in primary macrophage cultures severely reduced the ability of the macrophages to engulf apoptotic cells, and a dominant-negative form of RhoA enhanced the process. These results indicated that the efficient engulfment of apoptotic cells requires the concerted action of small GTPase family members. We demonstrated previously that NIH3T3 cells expressing the alphav beta3 integrin efficiently engulf apoptotic cells in the presence of milk fat globule epidermal growth factor 8 via a phosphatidylserine-dependent mechanism. The dominant-negative form of RhoG or Rac1 inhibited this process, which suggested RhoG and Rac1 are also involved in the integrin-mediated engulfment.
Nakaya
Michio
M
Department of Genetics, Osaka University Medical School, Osaka 565-0871, Japan.
Tanaka
Masato
M
Okabe
Yasutaka
Y
Hanayama
Rikinari
R
Nagata
Shigekazu
S
D000818:Animals; D017209:Apoptosis; D001854:Bone Marrow Cells / Q000166:cytology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D005260:Female; D015723:Gene Library; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D041681:NIH 3T3 Cells; D010587:Phagocytosis; D011994:Recombinant Proteins / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D014170:Transformation, Genetic; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D011994:Recombinant Proteins; D016173:Macrophage Colony-Stimulating Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020696:rab5 GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein