TY - JOUR A1 - Krautwald, Stefan A1 - Büscher, Dirk A1 - Jesenberger, Veronika A1 - Buder, Sylke A1 - Baccarini, Manuela T1 - Involvement of the protein tyrosine phosphatase SHP-1 in Ras-mediated activation of the mitogen-activated protein kinase pathway. JF - Mol Cell Biol. N2 - Ubiquitously expressed SH2-containing tyrosine phosphatases interact physically with tyrosine kinase receptors or their substrates and relay positive mitogenic signals via the activation of the Ras-mitogen-activated protein kinase (MAPK) pathway. Conversely, the structurally related phosphatase SHP-1 is predominantly expressed in hemopoietic cells and becomes tyrosine phosphorylated upon colony-stimulating factor 1 treatment of macrophages without associating with the colony-stimulating factor 1 receptor tyrosine kinase. Mice lacking functional SHP-1 (me/me and me(v)/me(v)) develop systemic autoimmune disease with accumulation of macrophages, suggesting that SHP-1 may be a negative regulator of hemopoietic cell growth. By using macrophages expressing dominant negative Ras and the me(v)/me(v) mouse mutant, we show that SHP-1 is activated in the course of mitogenic signal transduction in a Ras-dependent manner and that its activity is necessary for the Ras-dependent activation of the MAPK pathway but not of the Raf-1 kinase. Consistent with a role for SHP-1 as an intermediate between Ras and the MEK-MAPK pathway, Ras-independent activation of the latter kinases by bacterial lipopolysaccharide occurred normally in me(v)/me(v) cells. Our results sharply accentuate the diversity of signal transduction in mammalian cells, in which the same signaling intermediates can be rearranged to form different pathways. KW - Molecular Cell Biology KW - protein kinase pathway KW - Ras Y1 - 2020 U6 - http://dx.doi.org/doi: 10.1128/mcb.16.11.5955 VL - 1996 IS - 16(11) SP - 5955 EP - 5963 ER - TY - JOUR A1 - Jesenberger, Veronika A1 - Procyk, Katarzyna A1 - Yuan, Junying A1 - Reipert, Siegfried A1 - Baccarini, Manuela T1 - Salmonella-induced caspase-2 activation in macrophages: a novel mechanism in pathogen-mediated apoptosis JF - J Exp Med. N2 - The enterobacterial pathogen Salmonella induces phagocyte apoptosis in vitro and in vivo. These bacteria use a specialized type III secretion system to export a virulence factor, SipB, which directly activates the host's apoptotic machinery by targeting caspase-1. Caspase-1 is not involved in most apoptotic processes but plays a major role in cytokine maturation. We show that caspase-1-deficient macrophages undergo apoptosis within 4-6 h of infection with invasive bacteria. This process requires SipB, implying that this protein can initiate the apoptotic machinery by regulating components distinct from caspase-1. Invasive Salmonella typhimurium targets caspase-2 simultaneously with, but independently of, caspase-1. Besides caspase-2, the caspase-1-independent pathway involves the activation of caspase-3, -6, and -8 and the release of cytochrome c from mitochondria, none of which occurs during caspase-1-dependent apoptosis. By using caspase-2 knockout macrophages and chemical inhibition, we establish a role for caspase-2 in both caspase-1-dependent and -independent apoptosis. Particularly, activation of caspase-1 during fast Salmonella-induced apoptosis partially relies on caspase-2. The ability of Salmonella to induce caspase-1-independent macrophage apoptosis may play a role in situations in which activation of this protease is either prevented or uncoupled from the induction of apoptosis. KW - caspase-2 activation in macrophages KW - pathogen-activated apoptosis KW - Molecular Cell Biology Y1 - 2020 U6 - http://dx.doi.org/10.1084/jem.192.7.1035 VL - 2000 IS - 192(7) SP - 1035 EP - 1046 ER - TY - JOUR A1 - Jesenberger, Veronika A1 - Procyk, Katarzyna A1 - Rüth, Jochen A1 - Schreiber, Martin A1 - Theussl, Hans Christian A1 - Wagner, Erwin A1 - Baccarini, Manuela T1 - Protective Role of Raf-1 in Salmonella-Induced Macrophage Apoptosis JF - J Exp Med. N2 - Invasive Salmonella induces macrophage apoptosis via the activation of caspase-1 by the bacterial protein SipB. Here we show that infection of macrophages with Salmonella causes the activation and degradation of Raf-1, an important intermediate in macrophage proliferation and activation. Raf-1 degradation is SipB- and caspase-1–dependent, and is prevented by proteasome inhibitors. To study the functional significance of Raf-1 in this process, the c-raf-1 gene was inactivated by Cre-loxP–mediated recombination in vivo. Macrophages lacking c-raf-1 are hypersensitive towards pathogen-induced apoptosis. Surprisingly, activation of the antiapoptotic mitogen-activated protein kinase kinase (MEK)/extracellular signal–regulated kinase (ERK) and nuclear factor κB pathways is normal in Raf-1–deficient macrophages, and mitochondrial fragility is not increased. Instead, pathogen-mediated activation of caspase-1 is enhanced selectively, implying that Raf-1 antagonizes stimulus-induced caspase-1 activation and apoptosis. KW - Salmonella-Induced Macrophage Apoptosis KW - Raf-1 pathway KW - Molecular Cell Biology Y1 - 2020 U6 - http://dx.doi.org/10.1084/jem.193.3.353 VL - 2001 IS - 193(3) SP - 353 EP - 364 ER - TY - JOUR A1 - Jesenberger, Veronika A1 - Jentsch, Stefan T1 - Deadly encounter: ubiquitin meets apoptosis JF - Nat Rev Mol Cell Biol. N2 - The ubiquitin/proteasome pathway is the main non-lysosomal route for intracellular protein degradation in eukaryotes. It is instrumental to various cellular processes, such as cell-cycle progression, transcription and antigen processing. Recent findings also substantiate a pivotal role of the ubiquitin/proteasome pathway in the regulation of apoptosis. Regulatory molecules that are involved in programmed cell death have been identified as substrates of the proteasome. Moreover, key regulators of apoptosis themselves seem to have an active part in the proteolytic inactivation of death executors. KW - programmed cell death KW - Molecular Cell Biology Y1 - 2020 U6 - http://dx.doi.org/https://doi.org/10.1038/nrm731 VL - 2002 IS - 3(2) SP - 112 EP - 121 ER -