The Cleavage of Neutrophil Leukosialin (CD43) by Cathepsin G Releases Its Extracellular Domain and Triggers Its Intramembrane Proteolysis by Presenilin/γ-Secretase

Abstract

The highly negatively charged membrane sialoglycoprotein leukosialin, CD43, is shed during neutrophil activation. This is generally thought to enhance cell adhesion. We here describe two novel consequences of this shedding, during neutrophil activation by phorbol esters or by chemoattractants after TNF-␣ priming. CD43 proteolysis was investigated by Western blotting, using a polyclonal antibody to CD43 intracellular domain. Our data emphasize the importance of a juxtamembranous cleavage of about 50% of membrane CD43 molecules by cathepsin G. Indeed, it is inhibited by ␣1-antichymotrypsin and cathepsin G inhibitor I and is reproduced by exogenous purified cathepsin G. The resulting membrane-anchored C-terminal fragment, CD43-CTF, becomes susceptible to presenilin/␥-secretase, which releases CD43 intracytoplasmic domain: preincubation with three different ␥-secretase inhibitors, before PMN treatment by agonists or by purified cathepsin G, results in the accumulation of CD43-CTF. Because CD43 binds E-selectin, we also investigated the effect of the soluble extracellular domain CD43s, released by cathepsin G juxtamembranous cleavage, on neutrophil adhesion to endothelial cells. A recombinant CD43s-Fc fusion protein inhibited neutrophil E selectindependent adhesion to endothelial cells under flow conditions, while it had no effect on neutrophil static adhesion. We thus propose that, in addition to its potential pro-adhesive role, CD43 proteolysis results in: (i) the release, by cathepsin G, of CD43 extracellular domain, able to inhibit the adhesion of flowing neutrophils on endothelial cells and thus to participate to the natural control of inflammation; (ii) the release and/or the clearance, by presenilin/␥-secretase, of CD43 intracellular domain, thereby regulating CD43-mediated signaling.The regulated proteolysis of transmembrane proteins represents an important mechanism of cell functions modulation.The inflammation resolution involves, for example, the shedding of cytokine receptors and adhesion molecules, which down-regulates leukocyte adhesion to endothelium. These regulations result from a decreased membrane expression of receptors and/or from the release of soluble fragments, competing with their membrane counterparts. The majority of shed proteins identified to date are cleaved by metalloproteinases or by neutrophil-derived serine proteases (1). Leukosialin, CD43, is the predominant cell surface sialoprotein of leukocytes (2) and has both anti-adhesive and adhesive properties. Its function has been mainly studied on lymphocytes, where CD43 behaves both as a negative regulator of T cell proliferation and adhesion and as a positive regulator of memory T cell trafficking (3, 4). Although its expression is normally restricted to leukocytes, CD43 is present on colon carcinomas and on several nonhematopoietic cell lines (5, 6). In these cell lines, CD43 is processed by a presenilin/␥-secretase-mediated regulated intramembrane proteolysis (RIP) 3 (7). RIP refers to a sequential proteolysis of various type I membra...

Secretome analysis to elucidate metalloprotease‐dependent ectodomain shedding of glycoproteins during neuronal differentiation

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An Interactive Network of Elastase, Secretases, and PAR-2 Protein Regulates CXCR1 Receptor Surface Expression on Neutrophils

“…Besides amyloid precursor protein, secretases have been reported to play a role in cleaving and processing a variety of different proteins, including MHC class I proteins, in particular human leukocyte antigen A2 (31), the interleukin-1 receptor type 1 (IL-1R1) (32), leukosialin/ CD43 (33), transmembrane-associated chemokines, the Notch receptor, and others (34). These processes probably occur close to the cellular membrane through juxtamembranous cleavage events as demonstrated previously for CD43 (33). Despite the fact that our BRET and co-IP experiments supported a physical interaction of secretases with PAR-2 and CXCR1, further studies are required to dissect the precise sequence of molecular events involved in this proteolytic cascade.…”

CD43 processing and nuclear translocation of CD43 cytoplasmic tail are required for cell homeostasis

“…Processing of human CD43 by ␣-and ␥-secretases has been demonstrated in several carcinoma cell lines 18,21 and primary human neutrophils, 22 raising the possibility that CD43 might be functionally involved in regulated intramembrane proteolysisdependent signaling similarly to Notch-1. 23 For personal use only.…”