Protein degradation and apoptotic death in lymphocytes during Fiv infection: Activation of the ubiquitin-proteasome proteolytic system

The movement of a cell through the sequential phases of apoptosis is accomp anied by a progressive decrease in cell size with loss in protein mass. In lymphocytes from Hiv-infected persons, protein loss during apoptosis is due to increased protein degradation rather than decreased synthesis. To ident ify and characterize the proteolytic enzymes or enzyme systems involved in this process, we studied several features of protein turnover in lymphocyte s from peripheral blood and lymph nodes during the natural and experimental infection by feline immunodeficiency virus (Fiv), This animal model allowe d us to integrate in vivo results with in vitro observations of protein dam age. Here we report that protein breakdown in apoptotic cells is concomitan t with the activation of the ATP and ubiquitin-dependent multicatalytic sys tem (proteasome). We suggest that proteasome activation is part of the prot eolytic cascade in the execution phases of apoptosis in AIDS. (C) 1999 Acad emic Press.