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Mol Immunol. 2008 Apr;45(8):2127-37. doi: 10.1016/j.molimm.2007.12.015. Epub 2008 Mar 4.

Modulation of murine complement receptor type 2 (CR2/CD21) ectodomain shedding by its cytoplasmic domain.

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  • 1Biotechnology Institute Thurgau, 8280 Kreuzlingen, Switzerland.


Ectodomain shedding is a mechanism that regulates numerous functions of cell surface proteins. The extracellular domain of the human complement receptor 2 (CR2/CD21) is released by proteolytic cleavage as a soluble protein through a variety of stimuli including the thiol antioxidants N-acetylcysteine (NAC) and glutathione (GSH), and the oxidant pervanadate (PV). In addition, PV mimics B cell antigen receptor (BCR) signaling. Here, we show that murine CD21 is shed upon those stimuli and that the cytoplasmic domain is an important modulator for CD21-shedding. B cells expressing a mutant CD21 cytoplasmic domain with only three amino acids (KHR) showed increased CD21-shedding and required lower stimuli concentrations. At lower PV concentrations, wildtype CD21 was up-regulated on the cell surface, whereas at higher PV concentrations the ectodomain was shed. These findings further indicate that GSH and NAC utilize different pathways than PV to activate CD21-shedding. Altogether, as pre-activated B cells express higher CD21 levels than resting mature B cells or fully activated and antigen-experienced B cells, we suggest CD21-shedding to be a mechanism to fine-tune B cell activation.

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