CD93 interacts with the PDZ domain-containing adaptor protein GIPC: implications in the modulation of phagocytosis.
CD93 was originally identified as a myeloid cell-surface marker and subsequently associated with an ability to modulate phagocytosis of suboptimally opsonized immunoglobulin G and complement particles in vitro. Recent studies using mice deficient in CD93 have demonstrated that this molecule modulates phagocytosis of apoptotic cells in vivo. To investigate signal transduction mechanisms mediated by CD93, CD93 cytoplasmic tail (CYTO)-binding proteins were identified in a yeast two-hybrid screen. Fifteen of 34 positive clones contained a splice variant or a partial cDNA encoding GIPC, a PSD-95/Dlg/ZO-1 (PDZ) domain-containing protein, shown previously to regulate cytoskeletal dynamics. A single clone of the N-terminal kinase-like protein p105 and an uncharacterized stem cell transcript also showed specificity for binding to the CYTO by yeast two-hybrid. Using the yeast two-hybrid system and an in vitro glutathione S-transferase fusion protein-binding assay, the binding of GIPC to the CYTO was shown to involve a newly identified class I PDZ-binding domain in the CD93 carboxyl terminus. Four positively charged amino acids in the juxtamembrane domain of CD93 were shown to be critical in stabilizing these interactions. Treatment of human monocytes with a cell-permeable peptide encoding the C-terminal 11 amino acids of CD93 resulted in an enhancement of phagocytosis, supporting the hypothesis that this protein-protein interaction domain is involved in the modulation of phagocytosis. These protein interactions may participate as molecular switches in modulating cellular phagocytic activity.
Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA. sbohlson@uci.edu
Suzanne S
SS
Bohlson
Mingyu
M
Zhang
Christopher E
CE
Ortiz
Andrea J
AJ
Tenner
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009479:Neuropeptides / Q000378:metabolism*; D010587:Phagocytosis; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011951:Receptors, Complement / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D014471:Umbilical Veins / Q000166:cytology
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C115271:Gipc1 protein, mouse; D008562:Membrane Glycoproteins; D009479:Neuropeptides; D011951:Receptors, Complement; C032402:complement 1q receptor