Modulation of murine complement receptor type 2 (CR2/CD21) ectodomain shedding by its cytoplasmic domain.
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.
Hoefer
Melanie M
MM
Biotechnology Institute Thurgau, 8280 Kreuzlingen, Switzerland.
Aichem
Annette
A
Knight
Andrew M
AM
Illges
Harald
H
D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism*; D005453:Fluorescence; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D017464:Receptors, Complement 3d / Q000737:chemistry* / Q000378:metabolism*; D017384:Sequence Deletion; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013997:Time Factors; D014638:Vanadates / Q000494:pharmacology
D000975:Antioxidants; D017464:Receptors, Complement 3d; D013438:Sulfhydryl Compounds; C076715:pervanadate; D014638:Vanadates