Uncoupling protein 2 and 3 in marsupials: identification, phylogeny, and gene expression in response to cold and fasting in Antechinus flavipes

Abstract

We searched for the presence of uncoupling protein genes so far unknown in marsupials and monotremes and identified uncoupling protein 2 (UCP2) and UCP3 full-length cDNAs in libraries constructed from the marsupials Antechinus flavipes and Sminthopsis macroura. Marsupial UCP2 is 89-90% identical to rodent UCP2, whereas UCP3 exhibits 80% identity to mouse UCP3. A phylogenetic tree including all known UCPs positions the novel marsupial UCP2 and UCP3 at the base of the mammalian orthologs. In the 5'-untranslated region of UCP2 a second open reading frame encoding for a 36-amino acid peptide was identified which is highly conserved in all vertebrate UCP2 transcripts. Analysis of tissue specificity in A. flavipes with homologous cDNA probes revealed ubiquitous presence of UCP2 mRNA and striated muscle specificity of UCP3 mRNA resembling the known expression pattern in rodents. Neither UCP2 nor UCP3 gene expression was stimulated in adipose tissue and skeletal muscle of cold exposed A. flavipes. However, UCP3 mRNA expression was upregulated 6-fold in heart and 2.5-fold in skeletal muscle as reported for rodents in response to fasting. Furthermore, UCP3 mRNA seems to be coregulated with PDK4 mRNA, indicating a relation to enhanced lipid metabolism. In contrast, UCP2 gene expression was not regulated in response to fasting in adipose tissue and skeletal muscle but was diminished in the lung and increased in adipose tissue. Taken together, the sequence analysis, tissue specificity and physiological regulation suggest a conserved function of UCP2 and UCP3 during 130 million years of mammalian evolution.

Cost of transport is increased after cold exposure inMonodelphis domestica: training for inefficiency

“…It has been previously reported that UCP3 is not upregulated in rodent skeletal muscle following cold acclimation (Boss et al, 1997(Boss et al, , 1998), but Toyomizu et al (2002) reported that UCP3 expression is induced in the skeletal muscle of cold-exposed chickens. More recently, UCP3 was not induced in Antechinus flavipes, a similar sized Australian marsupial, although the period of cold exposure was short (Jastroch et al, 2004). Thus although equivocal, a role for UCP3 in muscle thermogenesis may be better elucidated in organisms in which skeletal muscle plays a primary role in thermogenesis.…”

The effects of fasting and cold exposure on metabolic rate and mitochondrial proton leak in liver and skeletal muscle of an amphibian, the cane toad Bufo marinus

“…As described previously (Jastroch et al, 2004), physical gene maps of verified UCP loci were scaled based on assemblies of the Ensembl Genome Browser. Genes located up-and downstream of UCP genes in these loci were blasted against human, mouse and zebrafish genomes for the highest score.…”

“…Total RNA was isolated using TRIzol (Gibco BRL), quantified and subjected to northern blot analysis as described previously (Jastroch et al, 2004). The membranes were hybridized using Xenopus laevis 251 bp UCP1 and 550 bp UCP2 cDNA probes derived with Xenopus tropicalis gene specific primers (UCP1: forward 5Ј-GGCTCC AGAGACAGATGAGCTTCGC-3Ј, reverse 5Ј-GGC -TATGGT TT TATAGGCGTCCATAGTGCC-3Ј; UCP2: forward 5Ј-GGTTCGG TTCCAAGCTCAGGCC-3Ј, reverse 5Ј-ATGGC -ACA GT TGATGGCGCTGG-3Ј).…”

Thermal sensitivity of uncoupling protein expression in polar and temperate fish

“…Homologues of UCP1 have been identified in various mammalian tissues Damon et al, 2000;Nakatani et al, 2002;Jastroch et al, 2004), but also in birds Vianna et al, 2001;Talbot et al, 2004), plants (Laloi et al, 1997;Maia et al, 1998;HourtonCabassa et al, 2004), protists (Jarmuszkiewicz et al, 1999) and fungi (Jarmuszkiewicz et al, 2000), thus suggesting a more central role for the UCP family in metabolism. The specific nature of the UCP isoforms as proton channels, however, is less well established.…”