Biochemical alteration of membrane-associated IL-6 RI (80-kDa) in adherent macrophages and vascular endothelium.
The potential biochemical mechanisms that mediate the 'shedding' of soluble IL-6 RI (80-kDa) receptor fragments in populations of adherent macrophages were explored. Stimulated macrophages displayed proportional increases in both the expression of membrane-associated IL-6 RI (80-kDa) and the release of soluble receptor fragments. The use of protease inhibitors implicated thiol/cysteine and carboxyl/aspartate proteases in this process. Cathepsin-D depleted membrane-associated IL-6 RI (80-kDa) complexes and generated soluble receptor fragments. A carboxyl/aspartate protease from activated macrophages isolated utilizing pepstatin-A affinity chromatography, was also found to affect membrane-associated IL-6 RI (80-kDa) complexes and generate soluble receptor fragments. Most likely, this fraction corresponded to cathepsin-D based upon its origin, pepstatin-A binding avidity, Hb-PAGE zymography, and hydrolysis of an enzyme-specific substrate. We conclude that cathepsin-D can generate soluble fragments of IL-6 RI (80-kDa) expressed by both macrophages and vascular endothelium.
Coyne
C P
CP
Veterinary Research Program, Veterinary Pharmacology Research Laboratory, College of Veterinary Medicine, Mississippi State University, Mississippi, USA. coyne@cvm.msstate.edu
Howell
T
T
Baravick
J
J
Baravick
E
E
Willetto
C
C
Fenwick
B W
BW
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D002021:Buffers; D000001:Calcimycin / Q000494:pharmacology; D002402:Cathepsin D / Q000037:antagonists & inhibitors*; D002417:Cattle; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D002951:Citrates; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D010436:Pepstatins / Q000494:pharmacology; D019947:Receptors, Interleukin-6 / Q000378:metabolism*; D000077559:Sodium Citrate
D002021:Buffers; D002951:Citrates; D015853:Cysteine Proteinase Inhibitors; D010436:Pepstatins; D019947:Receptors, Interleukin-6; C014195:Streptomyces pepsin inhibitor; D000077559:Sodium Citrate; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D016282:Aspartic Acid Endopeptidases; D002402:Cathepsin D; D007930:Leucine; C024974:E 64; C031375:pepstatin