Cholesterol-independent Interactions with CD47 Enhance αvβ3 Avidity

Abstract

Expression in OV10 cells of either wild-type CD47 or its extracellular IgV domain linked to a glycosylphosphatidylinositol anchor-(IgV-GPI) enhanced ligand-induced ␣ v ␤ 3 activation as detected by the binding of LIBS1 and LIBS6 mAbs. The amplitude of LIBS binding was greater with both CD47 and IgV-GPI expression, indicating an increase in the population of "activable" integrin molecules. Expression of either CD47 species also increased ␣ v ␤ 3 -mediated adhesion to vitronectin, and to surfaces coated with the anti-␤ 3 antibody AP3, because of enhanced clustering of ␣ v ␤ 3 as confirmed by chemical cross-linking. Cholesterol depletion with methyl-␤-cyclodextrin did not prevent the increase in anti-LIBS binding, but reduced cell adhesion to vitronectin and AP3. However, cells expressing CD47 were partially insulated against this disruption, and IgV-GPI was even more effective. Both CD47 and IgV-GPI were found in cholesterol-rich rafts prepared in the absence of detergent, but only CD47 could recruit ␣ v ␤ 3 and its associated signaling molecules to these domains. Thus CD47-␣ v ␤ 3 complexes in cholesterol-rich raft domains appear to engage in G i -dependent signaling whereas CD47-␣ v ␤ 3 interactions that lead to integrin clustering are also detergent resistant, but are insensitive to cholesterol depletion and do not require the transmembrane region of CD47.

Extracellular Calpains Increase Tubular Epithelial Cell Mobility

“…The increase in cyclic AMP resulted probably from the activation of adenylyl cyclase, given that our measurements were performed in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Furthermore, there have been reports that ␣ v ␤ 3 integrin and integrin-associated protein (CD47) may combine to form a functional seven-transmembrane complex, which associates with G i protein and,once activated, decreases cyclic AMP (39). Thus, ␣ v ␤ 3 -CD47-G i complexes could be involved in the control of adenylyl cyclase activity by ␣ v ␤ 3 engagement/disengagement.…”

A novel protein kinase C α-dependent signal to ERK1/2 activated by αVβ3 integrin in osteoclasts and in Chinese hamster ovary (CHO) cells

“…This compartment is believed to consist of membrane microdomains, denominated lipid rafts, that are enriched in cholesterol and glycosphingolipids, implicated in several processes, including signal transduction, endocytosis, membrane trafficking, cytoskeletal reorganization and pathogen entry (Munro, 2003;Pike, 2004). α V β 3 integrin may be accumulated in rafts (Triantafilou and Triantafilou, 2003), and its ligand-induced activation is enhanced by glycosyl phosphatidylinositol anchor (McDonald et al, 2004). Lipid raft integrity is required for receptor-mediated actin cytoskeleton reorganization and PKCα translocation (Becart et al, 2003) and the raft fraction is assumed to be important for the Ca 2+ signalling and the Ca 2+ -dependent association of classical PKC to these microdomains (Orito et al, 2001).…”

Inhibition of SRC family kinases reduces myeloid‐derived suppressor cells in head and neck cancer

“…Recent reports have indicated that CD47 and LYN affect the integrin activation signal. 35 The CD47/SIRPa axis negatively regulates human immunity by inhibiting MDSCs maturation. 36 Interestingly, Western blot analysis indicated that the CD47/ SIRPa axis was almost completely inhibited by dasatinib treatment (Fig.…”