This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Coyne, C.P. Articles by Chenney, E. Search for Related Content PubMed PubMed Citation Articles by Coyne, C.P. Articles by Chenney, E. Social Bookmarking                   What's this?

Alterations in membrane-associated CD14 expression and the simultaneous liberation of soluble CD14 fragment in adherent macrophages mediated by a leukocyte carboxyl/aspartate protease

Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, USA, coyne{at}cvm.msstate.edu

Trey Howell

Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, USA

Hrvoje Smodlaka

Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, USA

Carla Willetto

Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, USA

Brad W. Fenwick

Department of Pathobiology and Molecular Biology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA

Erle Chenney

Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, USA

Investigations sought to discover the biochemical mechanisms in macrophages that mediate the `shedding' of soluble CD14 fragment. Stimulated macrophages display both increased liberation of soluble CD14 fragment and decreases in residual membrane-associated CD14 complexes following exposure to activating agents (fMLP/A23187). Application of `class-specific' protease inhibitors revealed that a thiol/cysteine was involved in the biochemical production of soluble CD14 fractions and that a metalloprotease enzymatically degraded soluble CD14 fragment. Exposure of macrophages to individual proteases revealed that both cathepsin-D and elastase promoted variable depletion of membrane-associated CD14 complexes. Additionally, cathepsin-D, and to a lesser extent elastase, generated soluble CD14 fragment. Related studies isolated a carboxyl/aspartate protease from activated macrophages using pepstatin-A affinity chromatography. The physical and functional properties of macrophage pepstatin-A binding protein fractions closely corresponded with the known characteristics of cathepsin-D with respect to: (i) cellular origin; (ii) binding-avidity of carboxyl/aspartate proteases for pepstatin-A; (iii) non-specific proteolysis of haemoglobin detected by Hb-PAGE zymography; and (iv) hydrolysis of a synthetic cathepsin-D-specific peptide substrate. Interpretation of these findings collectively implies that activated leukocytes can biochemically alter membrane-associated CD14 complex expression and promote the liberation of soluble CD14 fragment in both activated and non-activated cell populations.

Journal of Endotoxin Research, Vol. 8, No. 4, 273-283 (2002)
DOI: 10.1177/09680519020080040401


CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?