A FAMILY OF SERINE PROTEASES EXPRESSED EXCLUSIVELY IN MYELO-MONOCYTICCELLS SPECIFICALLY PROCESSES THE NUCLEAR FACTOR-KAPPA-B SUBUNIT P65 IN-VITRO AND MAY IMPAIR HUMAN-IMMUNODEFICIENCY-VIRUS REPLICATION IN THESE CELLS

Two groups of U937 promonocytic cells were obtained by limiting diluti on cloning which differed strikingly in their ability to support human immunodeficiency virus 1 (HIV-1) replication. ''Plus'' clones replica ted the virus efficiently, whereas ''minus'' clones did not. We examin ed these clones for differences in nuclear factor (NF)-kappa B activit y which might account for the observed phenomenon. Stimulation of plus clones liberated the classical p50-p65 complex from cytoplasmic pools , whereas minus clones produced an apparently novel, faster-migrating complex, as judged by electrophoretic mobility shift assays. It is sur prising that the faster-migrating complex was composed also of p50 and p65. However, the p65 subunit was COOH-terminally truncated, as shown by immunoprecipitation. The truncation resulted from limited proteoly sis of p65 during cellular extraction which released particular lysoso mal serine proteases, such as elastase, cathepsin G, and proteinase 3. These specific proteases are coordinately expressed and were present exclusively in the minus U937 clones, but not in the plus clones, as d emonstrated in the case of cathepsin G. In addition, these proteases w ere detected in certain subclones of THP-1 and HL-60 cells and in prim ary monocytes, in each case correlating with the truncated form of p65 . We demonstrate in vitro cleavage of p65 by purified elastase and cat hepsin G. It is possible that particular serine proteases may have inh ibiting effects on the replication of HIV-1 in myelo-monocytic cells. The data also demonstrate that special precautions must be taken when making extracts from myelomonocytic cells.