IDENTIFICATION OF THE PROTEOLYTIC-ENZYME WHICH CLEAVES HUMAN P75 TNF RECEPTOR IN-VITRO

The extracellular domains of the human 55 and 75 kD TNF receptors (p55 and p75 TNF-R) are proteolytically cleaved to produce 30 and 40 kD so luble fragments, respectively. Ln this study, the enzymatic activity i nvolved in the cleavage of human p75 TNF-R, named TNF-R releasing enzy me (TRRE), was identified in the culture supernatant of PMA-stimulated THP-1 cells using an activity assay system established by our group. When THP-I cells were stimulated with PMA, TRRE was released rapidly i nto the supernatant, reaching maximal activity within 3 hours. The rel ease of TRRE into the culture supernatant depended on the concentratio n of PMA and FCS. TRRE activity was partially inhibited by chelating a gents, suggesting that TRRE may be a metalloprotease-like enzyme. This is the first successful attempt to establish a stable TRRE source wit h a reliable assay system. (C) 1996 Academic Press, Inc.