Abstract

The Na⁺-K⁺-ATPase is an essential transport enzyme expressed in all animal tissues, where it generates ion gradients to maintain membrane potential and drive the transport of other solutes. It also balances metabolism and body temperature. In this study, the characterization of three novel bovine ATP1B2 splice variants, designated as ATP1B2-AS1, ATP1B2-AS2, and ATP1B2-AS3, is discussed. All three novel splice isoforms were derived from a complete transcript (ATP1B2-complete) by alternative splicing. The pattern of splicing to produce the ATP1B2-AS1 and ATP1B2-AS2 isoforms was intron retention; these isoforms were found in liver, kidney, muscle and breast tissues. For the ATP1B2-AS3 isoform, splicing was by exon inclusion and this isoform was only found in muscle tissue. As demonstrated by real-time polymerase chain reaction, the isoforms were all expressed at significantly lower levels than the complete ATP1B2 gene transcript in all the tissues studied. After heat-stress, the expression levels of the different transcripts were lower in different tissues; however, the expression of the ATP1B2-complete transcript increased in heart and lung tissues. The results of this research provide some useful information for further studies into the function of the bovine ATP1B2 gene. Alternative splicing (AS) is recognized as the major contributor to protein diversity from limited gene pool. ATP1B2-AS2 was the splice of intron retention found from ATP1B2 in liver, kidney, muscle and breast tissues. In the study, ATP1B2-AS2 showed that many of the amino acid residues were in an unfavorable energy environment. It is interesting to speculate that this may be the perfect transcript to respond to heat-stress. So, AS may become the appropriate pathway to tackle heat-stress and reduce the economic losses in cows.

Key words: ATP1B2 gene, alternative splicing, alternative splicing mechanism.