1
|
He B, Zhang J, Wang Y, Li Y, Zou X, Liang B. Identification of cytochrome b5 CYTB-5.1 and CYTB-5.2 in C. elegans; evidence for differential regulation of SCD. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1863:235-246. [PMID: 29237573 DOI: 10.1016/j.bbalip.2017.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 12/02/2017] [Accepted: 12/07/2017] [Indexed: 01/04/2023]
Abstract
Unsaturated fatty acids (UFAs) play crucial roles in living organisms regarding development, energy metabolism, stress resistance, etc. The biosynthesis of UFAs starts from the introduction of the first double bond by stearoyl-CoA desaturase (SCD), converting saturated fatty acids (SFAs) to monounsaturated fatty acids (MUFAs). This desaturation is considered to be an aerobic process that requires cytochrome b5 reductase, cytochrome b5 and SCD. However, this enzyme system remains elusive in Caenorhabditis elegans. Here, we show that inactivation by RNAi knockdown or mutation (gk442189) of putative cytochrome b5 genes cytb-5.1 led to reduced conversion of C18:0 to C18:1(n-9) by SCD desaturases FAT-6/7 in C. elegans. On the contrary, cytb-5.2RNAi and cytb-5.2(gk113588) mutant worms showed decreased conversion of C16:0 to C16:1(n-7) by FAT-5 desaturase. Dietary supplementation with C18:1(n-9) and C18:2(n-6) also showed that CYTB-5.1 is likely required for the activity of FAT-6/7 desaturases, but not for FAT-1 to FAT-4 desaturases. Interestingly, co-immunoprecipitation (Co-IP) demonstrated that either FAT-7 or FAT-5 has ability to interact with both CYTB-5.1 and CYTB-5.2. Moreover, RNAi knockdown of cytb-5.1 upregulates the transcriptional and translational expression of fat-5 to fat-7, which may be due to the feedback induction by reduced C18:1(n-9) and downstream fatty acids. Furthermore, both CYTB-5.1 and CYTB-5.2 are involved in fat accumulation, fertility and lifespan in worms, which may be independent of changes in fatty acid compositions. Collectively, these findings for the first time reveal the differential regulation of various SCDs by distinct cytochrome b5 CYTB-5.1 and CYTB-5.2 in the biosynthesis of UFAs in C. elegans.
Collapse
Affiliation(s)
- Baoshen He
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China; Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Jingjing Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China; Department of Hepatobiliary Surgery, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China
| | - Yanli Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
| | - Yamei Li
- School of Life Sciences, University of Science and Technology of China, Hefei 230036, China
| | - Xiaoju Zou
- Department of Life Science and Biotechnology, Key Laboratory of Special Biological Resource Development and Utilization of University in Yunnan Province, Kunming University, Kunming 650214, China.
| | - Bin Liang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China; Department of Hepatobiliary Surgery, Affiliated Hospital of Guangdong Medical University, Zhanjiang 524001, China.
| |
Collapse
|
2
|
Borgese N, D'Arrigo A, De Silvestris M, Pietrini G. NADH-cytochrome b5 reductase and cytochrome b5 isoforms as models for the study of post-translational targeting to the endoplasmic reticulum. FEBS Lett 1993; 325:70-5. [PMID: 8513896 DOI: 10.1016/0014-5793(93)81416-w] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cytochrome b5 and NADH-cytochrome b5 reductase are integral membrane proteins with cytosolic active domains and short membrane anchors, which are inserted post-translationally into their target membranes. Both are produced as different isoforms, with different localizations, in mammalian cells. In the rat, the reductase gene generates two transcripts by an alternative promoter mechanism: a ubiquitous mRNA coding for the myristylated membrane-bound form, and an erythroid mRNA which generates both the soluble form and a nonmyristylated membrane-binding form. The available evidence indicates that the ubiquitous myristylated form binds to the cytosolic face of both outer mitochondrial membranes and ER. In contrast, two genes code for two homologous forms of cytochrome b5, one of which is found on outer mitochondrial membranes, the other on the ER. The gene specifying the ER form probably also generates an erythroid-specific mRNA by alternative splicing, which codes for soluble cytochrome b5. Possible molecular mechanisms responsible for the observed localizations of these different enzyme isoforms are discussed.
Collapse
Affiliation(s)
- N Borgese
- C.N.R. Center for Cytopharmacology, University of Milan, Italy
| | | | | | | |
Collapse
|
3
|
Giordano SJ, Steggles AW. Differential expression of the mRNAs for the soluble and membrane-bound forms of rabbit cytochrome b5. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1172:95-100. [PMID: 8439576 DOI: 10.1016/0167-4781(93)90274-h] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Total RNA was extracted from a variety of rabbit tissues and reverse transcribed for use in the polymerase chain reaction technique. Using primers designed to amplify the membrane-bound liver cytochrome b5 cDNA, products of two sizes were observed. Both hybridized strongly to a radiolabelled liver cytochrome b5 probe. Sequencing confirmed that the two types of cDNA product encoded the membrane-bound and the soluble forms of b5. Messenger RNA corresponding to the soluble cytochrome was detected in the lung, gallbladder and the adrenal gland, as well as in reticulocytes and bone marrow. This was an unexpected finding since the protein has been isolated only from erythrocytes. In contrast, membrane-bound cytochrome b5 mRNA was detected in all tissues tested, suggesting that the corresponding protein is ubiquitous in tissue distribution.
Collapse
Affiliation(s)
- S J Giordano
- Department of Biochemistry and Molecular Pathology, Northeastern Ohio Universities College of Medicine, Rootstown 44272
| | | |
Collapse
|
4
|
Borgese N, D'Arrigo A, De Silvestris M, Pietrini G. NADH-cytochrome b5 reductase and cytochrome b5. The problem of posttranslational targeting to the endoplasmic reticulum. Subcell Biochem 1993; 21:313-41. [PMID: 8256272 DOI: 10.1007/978-1-4615-2912-5_14] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- N Borgese
- CNR Center for Cytopharmacology, University of Milan, Italy
| | | | | | | |
Collapse
|
5
|
Takematsu H, Kozutsumi Y, Suzuki A, Kawasaki T. Molecular cloning of rabbit cytochrome b5 genes: evidence for the occurrence of two separate genes encoding the soluble and microsomal forms. Biochem Biophys Res Commun 1992; 185:845-51. [PMID: 1627141 DOI: 10.1016/0006-291x(92)91704-t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The rabbit genomic segments for the soluble cytochrome b5 (b5) and microsomal b5 were amplified and isolated, respectively, by means of the polymerase chain reaction using primers corresponding to various portions of the open reading frame of microsomal b5 cDNA. The DNA sequence analysis revealed that the soluble b5 gene has an extra 24 nucleotide long insert which encodes a C-terminal amino acid and a termination codon which are specific to the soluble b5. Except for the insert, the sequences of the soluble and microsomal b5 genes are identical with each other from the 5' end to the 3' end of the open reading frame of the microsomal b5 cDNA. Comparison of the genomic sequences with the cDNA sequences suggested that the soluble and microsomal genes are intronless within their open reading frames. These data indicate that rabbit soluble and microsomal b5 mRNAs are encoded by two highly conserved but separate genes.
Collapse
Affiliation(s)
- H Takematsu
- Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Japan
| | | | | | | |
Collapse
|
6
|
Zhang H, Somerville C. Soluble and membrane-bound forms of cytochrome b5 are the products of a single gene in chicken. Arch Biochem Biophys 1990; 280:412-5. [PMID: 2369133 DOI: 10.1016/0003-9861(90)90350-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In order to determine the relationship of the soluble cytochrome b5 found in erythrocytes to the membrane-bound form found in other tissues, a cDNA clone encoding cytochrome b5 in chicken erythrocytes was isolated by using mixed oligonucleotides based on a partial amino acid sequence of the protein. Complete nucleotide sequence identity between the erythrocyte cDNA and the sequence of a cDNA clone of the liver protein suggests that they are transcribed from the same gene. The isolation and structural analysis of genomic clones was also consistent with the presence of only one cytochrome b5 gene in chicken. These results suggest that the formation of soluble erythrocyte cytochrome b5 occurs by proteolytic processing of the membrane-bound form. Thus, previous reports indicating that the carboxyl terminal amino acid residue of the erythrocyte form differs from the corresponding residue of the membrane-bound form may suggest the existence of a novel post-translational modification.
Collapse
Affiliation(s)
- H Zhang
- DOE Plant Research Laboratory, Michigan State University, East Lansing 48824
| | | |
Collapse
|
7
|
Kimura S, Abe K, Sugita Y. Differences in C-terminal amino acid sequences between erythrocyte and liver cytochrome b5 isolated from pig and human. Evidence for two tissue-specific forms of cytochrome b5. FEBS Lett 1984; 169:143-6. [PMID: 6714421 DOI: 10.1016/0014-5793(84)80306-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Two forms of cytochrome b5, a soluble erythrocyte form and a membrane-bound liver form, were purified from pig and human, and structural differences between them were analyzed. Porcine and human erythrocyte cytochrome b5 consisted of 97 amino acid residues and contained the same catalytic domain structure (residues 1-96) as that of the corresponding liver cytochrome b5, but had one amino acid replacement at the C-terminus (residue 97). These results suggest that erythrocyte cytochrome b5 is not derived from the liver protein by proteolysis but a translational product from another distinct mRNA of cytochrome b5.
Collapse
|