title: Molecular analysis, tissue profiles, and seasonal patterns of cytosolic and mitochondrial GPDH in freeze-resistant rainbow smelt (Osmerus mordax).
abstract: Rainbow smelt (Osmerus mordax) is an anadromous teleost that, beginning in late fall, accumulates plasma glycerol in excess of 200 mM, which subsequently decreases in the spring. The activity of cytosolic glycerol-3-phosphate dehydrogenase (cGPDH) is higher (i) in liver of smelt than in that of Atlantic salmon and capelin (nonglycerol accumulators), (ii) in liver of smelt maintained at 1°C than in that of smelt held at 8°-10°C, and (iii) in smelt liver than in smelt muscle, heart, brain, or kidney. In addition, transcript levels of cGPDH in liver peak in December during the onset of glycerol production and then decline over the remainder of the season. There are four cGPDH protein isoforms in smelt liver that are present regardless of glycerol production status. A minimum of four cGPDH gene copies identified by Southern blotting provide adequate genetic potential to yield multiple protein isoforms. A full-length cDNA for smelt mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) was cloned and characterized. The 2,790-bp cDNA contains a 109-bp 5'UTR, a 2,193-bp open reading frame, and a 488-bp 3'UTR; transcripts are ubiquitously expressed in both warm- and cold-acclimated smelt tissues. Smelt mGPDH encodes a 730-aa protein that clusters with that of zebrafish and frog and contains several common structural motifs. mGPDH transcript levels generally increase late in the seasonal glycerol cycle, and mGPDH enzyme activity increases significantly during the glycerol decrease phase. Taken together, these findings suggest that liver cGPDH and mGPDH play a key role in the glycerol accumulation and decrease phases, respectively.
authors: Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7, Canada.
authors: Jason L
authors: JL
authors: Robinson
authors: Jennifer R
authors: JR
authors: Hall
authors: Mark
authors: M
authors: Charman
authors: K Vanya
authors: KV
authors: Ewart
authors: William R
authors: WR
authors: Driedzic
mesh_terms: D000064:Acclimatization; D000595:Amino Acid Sequence; D000818:Animals; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004586:Electrophoresis; D005615:Freezing; D018628:Gene Dosage; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D005990:Glycerol / Q000097:blood / Q000378:metabolism; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009523:Newfoundland and Labrador; D036441:Osmeriformes / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012474:Salmon / Q000378:metabolism; D012621:Seasons; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D020033:Protein Isoforms; D012333:RNA, Messenger; D005993:Glycerolphosphate Dehydrogenase; D005990:Glycerol