Caspase-mediated Cleavage of Insulin Receptor Substrate

Abstract

Apoptosis is an important mechanism for maintaining tissue homeostasis. The efficient induction and execution of apoptosis are essential for cell clearance in specific developmental situations. Insulin-like growth factor (IGF)-I is a survival factor for epithelial cells in the mammary gland, and its withdrawal or inhibition leads to apoptosis. In this paper we describe a novel mechanism that may lead to suppression of an IGF-I-mediated signaling pathway through cleavage of insulin receptor substrate (IRS). During the process of forced weaning, when mammary epithelial cells rapidly enter apoptosis in vivo, IRS-1 and IRS-2 disappear. We have used cultured mammary epithelial cells to demonstrate that IRS removal can be mediated through the action of caspase 10. Caspase 10 activation and IRS-1 cleavage are regulated by a MKK1-signaling pathway but not by a phosphatidylinositol-3 kinase pathway nor by the extracellular proapoptotic ligands FasL, tumor necrosis factor-␣-related apoptosis-inducing ligand (TRAIL), or transforming growth factor-␤3. In addition we show that the loss of IRS-1 after MKK1 inhibition prevents IGF-mediated phosphorylation of FKHRL1.

Oncogenic Transformation by the Signaling Adaptor Proteins Insulin Receptor Substrate (IRS)-1 and IRS-2

“…116 The dramatic changes in IRS protein levels occurred in the absence of any alteration in mRNA levels, indicating that this effect was post-transcriptional. 115 While we don't know the mechanisms of loss of IRS proteins during involution, Dr Streuli's group has shown that this maybe mediated by caspase 10 degradation, 117 and our studies would suggests that it maybe via proteasomal degradation. 110 We have performed limited experiments to assess IRS activity during mammary gland development.…”

Anamorsin, a Novel Caspase-3 Substrate in Neurodegeneration

“…The resulting reactant (9 l) was incubated with 50 ng of recombinant caspase-3 in the presence or absence of 50 M Z-VAD-fmk (a pan-caspase inhibitor) in 20 l of caspase reaction buffer (50 mM HEPES, 50 mM NaCl, 0.1% CHAPS, 10 mM EDTA, 5% glycerol, 10 mM dithiothreitol, pH 7.2) for 1.5 h at 37°C (28). To examine the specificity of caspase-3-mediated cleavage, the metabolically labeled mouse anamorsin wild type was incubated with 50 ng of recombinant human caspase-2, -7, and -8 (R&D Systems, Minneapolis, MN) or recombinant human caspase-6 and -9 (Enzo Life Sciences, Plymouth Meeting, PA).…”

Apaf-1 and caspase-9 deficiency prevents apoptosis in a Bax-controlled pathway and promotes clonogenic survival during paclitaxel treatment

“…Although some reports have implicated caspase-10 in apoptosis of murine cells, [25][26][27] there is clear evidence that the caspase-10 gene is absent in the mouse genome. 28,29 Therefore, we wondered whether paclitaxel could induce apoptosis in murine cells or, alternatively, trigger other death mechanisms.…”