Abstract
Ceramide is synthesized in yeast by two redundant acyl-CoA dependent synthases, Lag1 and Lac1. In lag1∆ lac1∆ cells, free fatty acids and sphingoid bases are elevated, and ceramides are produced through the redundant alkaline ceramidases Ypc1 and Ydc1, working backwards. Even with all four of these genes deleted, cells are surviving and continue to contain small amounts of complex sphingolipids. Here we show that these residual sphingolipids are not synthesized by YPR114w or YJR116w, proteins of unknown function showing a high degree of homology to Lag1 and Lac1. Indeed, the hextuple lag1∆ lac1∆ ypc1∆ ydc1∆ ypr114w∆ yjr116w∆ mutant still contains ceramides and complex sphingolipids. Yjr116w∆ exhibit an oxygen-dependent hypersensitivity to Cu2+ due to an increased mitochondrial production of reactive oxygen species (ROS) and a mitochondrially orchestrated programmed cell death in presence of copper, but also a general copper hypersensitivity that cannot be counteracted by the antioxidant N-acetyl-cysteine (NAC). Myriocin efficiently represses the synthesis of sphingoid bases of ypr114w∆, but not its growth. Both yjr116w∆ and ypr114w∆ have fragmented vacuoles and produce less ROS than wild type, before and after diauxic shift. Ypr114w∆/ypr114w∆ have an increased chronological life span. Thus, Yjr116w and Ypr114w are related, but not functionally redundant.
Highlights
To find out if Ypr114w and Yjr116w can act as ceramide synthases and are responsible for the persistence of complex sphingolipids in W303.4Δ cells [10,14], we deleted these genes in W303.4Δ trp5::SLC1-1 (= 4Δ) cells, generating the 4Δ.W303 trp5::SLC1-1 ypr114wΔ yjr116wΔ (= 6Δ) strain (Table B in S1 File)
The main intent of our report was to put to the test our educated guess, namely that the LAG1 homologs YJR116w and YPR114w would be responsible for residual ceramide and IPC synthesis in 4Δ cells [14]
Experiments say that the 4Δ and 6Δ cells contain the same amounts of ceramides, IPCs and MIPCs including low amounts of species with 44 C atoms
Summary
They act as messengers regulating the proliferation, survival, aging and death of cells [1,2]. The long chain bases (LCBs) dihydrosphingosine (DHS) and its 4-hydroxy derivative, phytosphingosine (PHS) are made and attached to fatty acids to form ceramides in the ER. The biosynthesis of inositolphosphorylceramides (IPCs) and more complex sphingolipids is believed to occur in the Golgi. Ceramide is an intermediate in the formation of complex sphingolipids. The acyl-CoA dependent biosynthesis of ceramide is operated by Lag and Lac (Fig 1A), two highly homologous and functionally redundant ER proteins, which are only
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.