TAILIEUCHUNG - Báo cáo khóa học: CD38 is expressed as noncovalently associated homodimers on the surface of murine B lymphocytes

CD38 is a transmembrane glycoprotein that functions as an ectoenzyme and as a receptor. Based on the structural similarity between CD38 and ADP-ribosyl cyclase from Aplysia californica, it was hypothesized that CD38 is expressed as a homodimer on the surface of cells. Indeed, CD38 dimers have been reported, however, the structural requirements for their stabilization on the plasma mem-brane are unknown. We demonstrate that the majority of CD38 is assembled as noncovalently associated homo-dimers on the surface of B cells | Eur. J. Biochem. 271 1025-1034 2004 FEBS 2004 doi CD38 is expressed as noncovalently associated homodimers on the surface of murine B lymphocytes Miguel E. Moreno-Garcia1 2 Santiago Partida-Sanchez3 Julie Primack3 Adriana Sumoza-Toledo2 Helene Muller-Steffner4. Francis Schuber4 Norman ODDenheimer5 Frances E Lund3 and . LeoDoldo Santos-Argumedo2 1 Departamentos de Biologia Celular and 2Biomedicina Molecular CINVESTAV-IPN Mexico 2Trudeau Institute Saranac Lake New York USA 4Laboratoire de Chimie Bioorganique UMR 7514 CNRS ULP Strasbourg-Illkirch France 5Department of Pharmaceutical Chemistry UCSF San Francisco USA CD38 is a transmembrane glycoprotein that functions as an ectoenzyme and as a receptor. Based on the structural similarity between CD38 and ADP-ribosyl cyclase from Aplysia californica it was hypothesized that CD38 is expressed as a homodimer on the surface of cells. Indeed CD38 dimers have been reported however the structural requirements for their stabilization on the plasma membrane are unknown. We demonstrate that the majority of CD38 is assembled as noncovalently associated homodimers on the surface of B cells. Analysis of CD38 mutants expressed in Ba F3 cells revealed that truncation of the cytoplasmic region or mutation of a single amino acid within the a1-helix of CD38 decreased the stability of the CD38 homodimers when solubilized in detergent. Cells expressing the unstable CD38 homodimers had diminished expression of CD38 on the plasma membrane and the half-lives of these CD38 mutant proteins on the plasma membrane were significantly reduced. Together these results show that CD38 is expressed as noncova-lently associated homodimers on the surface of murine B cells and suggest that appropriate assembly of CD38 homodimers may play an important role in stabilizing CD38 on the plasma membrane of B cells. Keywords B lymphocytes CD38 homodimer stability NAD glycohydrolase protein structure. CD38 is a type II .

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