Cloning,characterization, hypoxia and heat shock response of hypoxia inducible factor-1 (HIF-1) from the small abalone Haliotis diversicolor

In this study, hypoxia inducible factor-1α (HIF-1α) and hypoxia inducible factor-1β (HIF-1β) from small abalone Haliotis diversicolor were cloned. The cDNA of H. diversicolor HIF-1α (HdHIF-1α) is 2833 bp encoding a protein of 711aa and H. diversicolor HIF-1β (HdHIF-1β) is 1919 bp encoding a protein of 590aa. Similar to other species' HIF-1, HdHIF-1 has one basic helix–loop–helix (bHLH) domain and two Per-Arnt-Sim (PAS) domains, and HdHIF-1α has a oxygen-dependent degradation domain (ODDD) with two proline hydroxylation motifs and a C-terminal transactivation domain (C-TAD) with an asparagine hydroxylation motif. Under normoxic conditions, HdHIF-1α and HdHIF-1β mRNAs were constitutively present in all examined tissues. Under hypoxia (2.0 mg/L DO at 25 °C) stress, HdHIF-1α expression was up-regulated in gills at 4 h, 24 h and 96 h, and in hemocytes at 24 h and 96 h, while HdHIF-1β remained relatively constant. Under thermal stress (31 °C), HdHIF-1α expression was significantly increased in gills at 4 h, and hemocytes at 0 h and 4 h, while HdHIF-1β expression still remained relatively constant. These results suggested that HIF-1α may play an important role in adaption to poor environment in H. diversicolor.     

Cx40.8, a Cx43-like protein, forms gap junction channels inefficiently and may require Cx43 for its association at the plasma membrane

In addition to having a Cx43 ortholog, the zebrafish genome also contains a Cx43-like gene, Cx40.8. Here, we investigate the expression of cx40.8 in zebrafish fins and the function of Cx40.8 in HeLa cells. We find that cx40.8 is present in the same population of dividing cells as cx43. Unlike Cx43, dye coupling assays suggest that Cx40.8 only inefficiently forms functional gap junction channels. However, co-transfection reveals that Cx40.8 can co-localize with Cx43 in gap junction plaques, and that the resulting plaques contain functional gap junction channels. Together, these data suggest the possibility that Cx40.8 may functionally interact with Cx43 to regulate cell proliferation in vivo.

Structured summary

MINT-7266123: cx40.8 (genbank_protein_gi:68354404) and cx43 (uniprotkb:O57474) colocalize (MI:0403) by fluorescence microscopy (MI:0416)     

Functional Characterization of Oculodentodigital Dysplasia-Associated Cx43 Mutants

Oculodentodigital dysplasia (ODDD) is associated with at least 28 connexin43 (Cx43) mutations. We characterized four of these mutants; Q49K, L90V, R202H, and V216L. Populations of these GFP-tagged mutants were transported to the cell surface in Cx43-negative HeLa cells and Cx43-positive NRK cells. Dual patch-clamp functional analysis in N2A cells demonstrated that channels formed by each mutant have dramatically reduced conductance. Dye-coupling analysis revealed that each mutant exhibits a dominant-negative effect on wild-type Cx43. Since ODDD patients display skeletal abnormalities, we examined the effect of three other Cx43 mutants previously shown to exert dominant-negative effects on wild-type Cx43 (G21R, G138R, and G60S) in neonatal calvarial osteoblasts. Differentiation was unaltered by expression of these mutants as alkaline phosphatase activity and extent of culture mineralization were unchanged. This suggests that loss-of-function Cx43 mutants are insufficient to deter committed osteoblasts from their normal function in vitro. Thus, we hypothesize that the bone phenotype of ODDD patients may result from disrupted gap junctional intercellular communication earlier in development or during bone remodeling.