Hypoxia-inducible factor 1α from a high-altitude fish enhances cytoprotection and elevates nitric oxide production in hypoxic environment.

ABSTRACT

Hypoxia-inducible factors (HIFs) are master transcription factor regulating hypoxic responses in vertebrates. Species of Schizothoracine, a sub-family of cyprinidae, are highly endemic to the hypoxic Qinghai-Tibetan Plateau (QTP). What roles the HIFs play in hypoxic adaptation in the Schizothoracine fish is little known. In this study, the HIF-1α/B gene from Gymnocypris dobula (Gd) was characterized. The predicted protein for Gd-HIF-1α/B contains the main domains (bHLH, PAS, PAC, ODD, N-TAD, and C-TAD). Moreover, a specific mutation that the proline hydroxylation motif (LXXLAP) mutated into PxxLAP was observed in Gd-HIF-1α/B CODD domain, which may lead to changes in the function. To clarify whether HIF-1α/B of G. dobula possesses hypoxic adaptive features, Gd-HIF1α/B and Schizothorax prenanti-HIF1α/B (Sp-HIF1α/B) were cloned into an expression vector and transfected into 293T cells. Cell viability was found to be significantly higher in cells transfected with Gd-HIF-1α/B than those transfected with Sp-HIF-1α/B under hypoxic conditions. In addition, G. dobula HIF-1α/B showed stronger activity in transactivating the expression of nitric oxide (NO)-synthesizing enzyme, NOS2B under hypoxia stresses than the orthologous gene from S. prenanti, which were accompanied with upregulated expressions of NOS2B in heart of G. dobula, which may attribute to elevated NO levels detected in G. dobula than the lower land species. These results indicated that the HIF-1α plays an important role in mediating the iNOS signaling system in the process of evolutionary adaptation of the Schizothoracine to the highland environment.