title: Oxygen-sensitive mitochondrial accumulation of cystathionine β-synthase mediated by Lon protease.
abstract: Oxygen-sensitive accumulation and degradation, two opposite but intrinsically linked events, of heme proteins in mitochondria affect mitochondrial functions, including bioenergetics and oxygen-sensing processes. Cystathionine β-synthase (CBS) contains a prosthetic heme group and catalyzes the production of hydrogen sulfide in mammalian cells. Here we show that CBS proteins were present in liver mitochondria at a low level under normoxia conditions. Ischemia/hypoxia increased the accumulation of CBS proteins in mitochondria. The normalization of oxygen partial pressure accelerated the degradation of CBS proteins. Lon protease, a major degradation enzyme in mitochondrial matrix, recognized and degraded mitochondrial CBS by specifically targeting at the oxygenated heme group of CBS proteins. The accumulation of CBS in mitochondria increased hydrogen sulfide production, which prevented Ca(2+)-mediated cytochrome c release from mitochondria and decreased reactive oxygen species generation. Mitochondrial accumulation of heme oxygenase-1, another heme protein, was also regulated by oxygen level and Lon protease in the same mechanism as for CBS. Our findings provide a fundamental and general mechanism for oxygen-sensitive regulation of mitochondrial functions by linking oxygenation level to the accumulation/degradation of mitochondrial heme proteins.
authors.affiliation: Department of Biology, Lakehead University, Thunder Bay, ON, Canada P7B 5E1.
authors.forename: Huajian
authors.initials: H
authors.lastname: Teng
authors.forename: Bo
authors.initials: B
authors.lastname: Wu
authors.forename: Kexin
authors.initials: K
authors.lastname: Zhao
authors.forename: Guangdong
authors.initials: G
authors.lastname: Yang
authors.forename: Lingyun
authors.initials: L
authors.lastname: Wu
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
mesh_terms: D000818:Animals; D003541:Cystathionine beta-Synthase / Q000378:metabolism*; D057809:HEK293 Cells; D006418:Heme / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D049070:Protease La / Q000378:metabolism*; D059748:Proteolysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; D006418:Heme; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat; D049070:Protease La; D003541:Cystathionine beta-Synthase; D010100:Oxygen; D006862:Hydrogen Sulfide
keywords: gasotransmitter; hepatocytes; mitochondrial swelling; signaling; transfection