• Molecules and Cells
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• v.46 no.9
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• pp.545-557
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• 2023

Sphingomyelinase (SMase) catalyzes ceramide production from sphingomyelin. Ceramides are critical in cellular responses such as apoptosis. They enhance mitochondrial outer membrane permeabilization (MOMP) through self-assembly in the mitochondrial outer membrane to form channels that release cytochrome c from intermembrane space (IMS) into the cytosol, triggering caspase-9 activation. However, the SMase involved in MOMP is yet to be identified. Here, we identified a mitochondrial Mg²⁺-independent SMase (mt-iSMase) from rat brain, which was purified 6,130-fold using a Percoll gradient, pulled down with biotinylated sphingomyelin, and subjected to Mono Q anion exchange. A single peak of mt-iSMase activity was eluted at a molecular mass of approximately 65 kDa using Superose 6 gel filtration. The purified enzyme showed optimal activity at pH of 6.5 and was inhibited by dithiothreitol and Mg²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Fe²⁺, and Fe³⁺ ions. It was also inhibited by GW4869, which is a non-competitive inhibitor of Mg²⁺-dependent neutral SMase 2 (encoded by SMPD3), that protects against cytochrome c release-mediated cell death. Subfractionation experiments showed that mt-iSMase localizes in the IMS of the mitochondria, implying that mt-iSMase may play a critical role in generating ceramides for MOMP, cytochrome c release, and apoptosis. These data suggest that the purified enzyme in this study is a novel SMase.

• Korean Journal of Poultry Science
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• v.41 no.4
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• pp.287-296
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• 2014

Chicken eggs undergo various physiological changes during egg maturation. To study genes associated with the egg maturation in pre-ovulation (immature) and post-ovulation (mature), we compared gene expression patterns between in the immature egg and mature egg using RNA sequencing data. Mature and immature eggs were obtained from a Heuksaek Jaerae-jong of Korean native chicken. Total RNAs obtained from the eggs were sequenced by Illumina HiSeq 2000 platform, and the generated sequence reads were mapped to Galgal4 reference sequence assembly using Tuxedo Protocol. From the comparison of the RNA sequencing data, 315 genes were differentially expressed between mature and immature eggs, and 46 genes were only detected in immature egg. Further gene ontology (GO) analysis was performed for the differentially expressed genes using DAVID, showing that 29 and 28 GO terms were independently clustered from mature and immature, respectively. From those clustered GO terms, genes related to germ cell development, sex differentiation and defense response to bacterium were mainly expressed in the immature egg, while genes related to regulation of apoptosis, steroid metabolic process and lipid homeostasis were mainly detected in the mature egg. Our results could contribute to understand egg maturation before and after ovulation, and develop genetic markers for improving egg quality and productivity.

• Journal of Life Science
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• v.34 no.7
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• pp.443-452
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• 2024

This study aimed to examine the influence of 3,6-anhydroxygalactose (L-AHG) on the pro-inflammatory M1 polarization and pro-inflammatory responses observed in the RAW264.7 mouse macrophage cell line following stimulation with lipopolysaccharides (LPS). L-AHG exhibited a significant and dose-dependent inhibition of inducible nitric oxide synthase (iNOS) expression, a hallmark of M1 polarization, and subsequent NO production in LPS-stimulated RAW264.7 cells. Furthermore, the LPS-induced upregulation of cyclooxygenase-2 (COX-2), which drives the production of prostaglandin E2, an inflammatory mediator, was also inhibited by L-AHG. L-AHG did not affect the LPS-triggered Toll-like receptor 4 (TLR4)-mediated pro-inflammatory signaling pathway, which culminated in the activation of transforming growth factor-β-activated kinase 1 (TAK1). However, it was observed to inhibit the generation of reactive oxugen species (ROS) in a dose-dependent manner, as well as the TAK1-driven activation of JNK and p38 MAPK. Given that the active p38 MAPK is known to contribute to the assembly of active nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which catalyzes the intracellular generation of pro-inflammatory ROS in LPS-stimulated macrophages, the dose-dependent reduction in the LPS-induced ROS generation by L-AHG may be mainly due to the prevention of TAK1-driven activation of p38 MAPK. Together, these results demonstrate that the L-AHG-mediated inhibition of the TAK1-JNK/p38 MAPK activation phase of the pro-inflammatory signaling pathway in LPS-stimulated RAW264.7 cells by L-AHG represents a promising mechanism for suppressing M1 polarization and pro-inflammatory responses in macrophages.