RESUMO
In ischemic stroke, cytosolic death pathways are activated in injured neurons destined to die. Neuronal injury is modulated by cell surface receptors, among which the tumor necrosis factor receptor family obtained particular interest. Cytokine response modifier A (CrmA) is a cowpox virus-derived caspase inhibitor, which interferes with the so-called death-inducing signaling complex, thereby blocking receptor-mediated apoptosis. To elucidate CrmA's therapeutic potential in ischemic stroke, we characterized a transgenic mouse line expressing CrmA under a Thy1 promoter, which we subjected to intraluminal middle cerebral artery (MCA) occlusion. Using in situ hybridization histochemistry and Western blots, we show that the crmA gene integrated into chromosome 8 of the mouse genome, CrmA being expressed in the cerebral cortex and striatum. Although robustly expressed, transgenic CrmA did not influence ischemic injury, both when relatively long-lasting (90 min) and mild (30 min) MCA occlusions were imposed. As such, neither infarct volume, brain swelling or neurological deficits following 90-min ischemia, nor disseminated neuronal injury or caspase-3 activation following 30-min ischemia were influenced by CrmA. Our data argue against a therapeutic effect of CrmA in ischemic stroke.
Assuntos
Regulação da Expressão Gênica/fisiologia , Infarto da Artéria Cerebral Média/metabolismo , Infarto da Artéria Cerebral Média/prevenção & controle , Serpinas/metabolismo , Proteínas Virais/metabolismo , Animais , Animais Recém-Nascidos , Comportamento Animal , Encéfalo/metabolismo , Encéfalo/patologia , Edema Encefálico/etiologia , Edema Encefálico/patologia , Caspase 3/metabolismo , Caspase 8/metabolismo , Sobrevivência Celular , Modelos Animais de Doenças , Ativação Enzimática , Regulação da Expressão Gênica/genética , Técnicas In Vitro , Infarto da Artéria Cerebral Média/genética , Infarto da Artéria Cerebral Média/patologia , Camundongos , Camundongos Transgênicos , Serpinas/genética , Antígenos Thy-1/metabolismo , Proteínas Virais/genéticaRESUMO
Homologues of signal peptide peptidase (SPPLs) are putative aspartic proteases that may catalyse regulated intramembrane proteolysis of type II membrane-anchored signalling factors. Here, we show that four human SPPLs are each sorted to a different compartment of the secretory pathway. We demonstrate that SPPL2a and SPPL2b, which are sorted to endosomes and the plasma membrane, respectively, are functional proteases that catalyse intramembrane cleavage of tumour necrosis factor alpha (TNFalpha). The two proteases promoted the release of the TNFalpha intracellular domain, which in turn triggers expression of the pro-inflammatory cytokine interleukin-12 by activated human dendritic cells. Our study reveals a critical function for SPPL2a and SPPL2b in the regulation of innate and adaptive immunity.