Magic™ Anti-CASP9 polyclonal antibody

CASP9 (caspase 9) is a well-known initiator caspase which triggers intrinsic apoptosis. Recent studies also suggest various non-apoptotic roles of CASP9, including macroautophagy/autophagy regulation. However, the involvement of CASP9 in autophagy and its molecular mechanisms are not well understood. Here we report the non-apoptotic function of CASP9 in positive regulation of autophagy through maintenance of mitochondrial homeostasis. Growth factor or amino acid deprivation-induced autophagy activated CASP9, but without apoptotic features. Pharmacological inhibition or genetic ablation of CASP9 decreased autophagy flux, while ectopic expression of CASP9 rescued autophagy defects. In CASP9 knockout (KO) cells, initiation and elongation of phagophore membranes were normal, but sealing of the membranes and autophagosome maturation were impaired, and the lifetime of autophagosomes was prolonged. Ablation of CASP9 caused an accumulation of inactive ATG3 and decreased lipidation of the Atg8-family members, most severely that of GABARAPL1. Moreover, it resulted in abnormal mitochondrial morphology with depolarization of the membrane potential, reduced reactive oxygen species production, and aberrant accumulation of mitochondrial fusion-fission proteins. CASP9 expression or exogenously added H2O2 in the CASP9 KO cells corrected the ATG3 level and lipidation status of Atg8-family members, and restored autophagy flux. Of note, only CASP9 expression but not H2O2 rescued mitochondrial defects, revealing regulation of mitochondrial homeostasis by CASP9. Our findings suggest a new regulatory link between mitochondria and autophagy through CASP9 activity, especially for the proper operation of the Atg8-family conjugation system and autophagosome closure and maturation.

This study aimed to evaluate the effect of taurine (tau) supplementation to low fishmeal (FM) diets on growth performance, oxidative status, and immune response of European seabass juveniles. Four isoproteic (46% crude protein) and isolipidic (19% crude lipid) diets were formulated to contain either 25 or 12.5% FM and a mixture of plant feedstuffs, supplemented or not with 1% tau. Twelve groups of 20 fish (IBW = 9.4 g) were fed each diet for 9 weeks. Reduction of dietary FM from 25 to 12.5% impaired growth performance, feed efficiency, and protein efficiency ratio but had no effect on nitrogen retention (% N intake). Independently of FM level, dietary tau supplementation improved growth performance and nitrogen retention without affecting feed efficiency. Dietary FM level reduction increased liver G6PDH activity, but did not affect lipid peroxidation or activities of redox key enzymes. Contrarily, dietary tau supplementation decreased hepatic G6PDH and GPX activities and lipid peroxidation. Gene expression COX-2 was not affected either by FM or tau levels but TNF-alpha increased with the reduction of FM level but not with the tau level. Dietary tau supplementation decreased Casp3 and Casp9 expression regardless of dietary FM level. Overall, this study evidenced that dietary tau supplementation improved growth performance and antioxidant response and reduced intestine inflammatory and apoptosis processes.