Skeletal Muscle Proteome Analysis Provides Insights on High Altitude Adaptation of Yaks

The differences in proteome profile of longissimus thoracis (LT) muscles of yak (Bos grunniens) and cattle (Bos taurus) were investigated employing isobaric tag for relative and absolute quantification (iTRAQ) approach to identify differentially expressed proteins and to understand the cellular level adaptations of yaks to high altitudes. Fifty-two proteins were differentially expressed in the two species, among which 20 were up-regulated and 32 were down-regulated in yaks. Gene ontology (GO) annotation revealed that most of the differentially expressed proteins were involved in the molecular function of protein binding, catalytic activity, and structural activity. Protein-protein interaction analysis recognized 24 proteins (involved in structural integrity, calcium ion regulation, and energy metabolism), as key nodes in biological interaction networks. These findings indicated that mammals living at high altitudes could possibly generate energy by pronounced protein catabolism and glycolysis compared with those living in the plains. The key differentially expressed proteins included calsequestrin 1, prostaglandin reductase 1 and ATP synthase subunit O, which were possibly associated with the cellular and biochemical adaptation of yaks to high altitude. These key proteins may be exploited as candidate proteins for mammalian adaptation to high altitudes.