title: Differential regulation of soluble and membrane CD40L proteins in T cells.
abstract: CD40 ligand is an important immunoregulatory protein expressed by T cells. This protein exists as two isoforms, a membrane glycoprotein and a truncated soluble form. Here we demonstrate that membrane and soluble CD40L (sCD40L) are differentially regulated depending upon the activation stimulus. In T cell receptor activated cells, both membrane and sCD40L proteins are expressed and CD28 costimulation further increases their expression. The dissection of TCR generated signals into calcium and PKC-dependent pathways demonstrates that calcium is sufficient to induce membrane CD40L yet insufficient for sCD40L. In contrast, sCD40L is preferentially induced by PKC. Moreover, sCD40L production is blocked by Zn(2+)-dependent metalloproteinase inhibitors while membrane CD40L is concurrently increased. This profile suggests the potential involvement of the ADAM-10 protease which was subsequently shown to cleave membrane CD40L to generate sCD40L. Given the role of sCD40L in numerous disease pathologies and its ability to activate proximal and distal immune responses, the regulated cleavage of CD40L may likely contribute to disease mechanisms.
authors.affiliation: Boise State University, Biology Department, Boise, ID 83725, USA.
authors.forename: Kelli M G
authors.initials: KM
authors.lastname: Matthies
authors.forename: Jodie L
authors.initials: JL
authors.lastname: Newman
authors.forename: Alma
authors.initials: A
authors.lastname: Hodzic
authors.forename: Denise G
authors.initials: DG
authors.lastname: Wingett
mesh_terms: D018106:CD28 Antigens / Q000502:physiology; D017252:CD3 Complex / Q000502:physiology; D023201:CD40 Ligand / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology; D008565:Membrane Proteins / Q000378:metabolism*; D012995:Solubility; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D018106:CD28 Antigens; D017252:CD3 Complex; D008024:Ligands; D008565:Membrane Proteins; D023201:CD40 Ligand