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Molecular and functional characterization of catfish (Heteropneustes fossilis) aquaporin-1b: changes in expression during ovarian development and hormone-induced follicular maturation.

Abstract：

:The oocytes of the freshwater catfish Heteropneustes fossilis hydrate during hormone-induced meiotic maturation. To investigate if this process may be mediated by aquaporins (AQPs), as it occurs in marine fish producing highly hydrated eggs, the cloning of ovarian AQPs in catfish was carried out. Using degenerate primers for conserved domains of the major intrinsic protein (MIP) family, and 5' and 3'end amplification procedures, a full-length cDNA encoding for an AQP1-like protein was isolated. The predicted protein showed the typical six transmembrane domains and two Asn-Pro-Ala (NPA) motifs conserved among the members of the AQP superfamily. Phylogenetic analysis indicated that the catfish AQP clustered with the teleost-specific aquaporin-1b subfamily, and accordingly it was termed HfAqp1b. Heterologous expression in Xenopus laevis oocytes indicated that HfAqp1b encoded for a functional AQP, water permeability being enhanced by cAMP. Site-directed mutagenesis revealed that cAMP induced the translocation of HfAqp1b into the oocyte plasma membrane most likely through the phosphorylation of HfAqp1b Ser(227). In adult catfish, hfaqp1b transcripts were detected exclusively in ovary and brain and showed significant seasonal variations; in the ovary, hfaqp1b was maximally expressed during the pre-spawning period, whereas in the brain the highest expression was detected during spawning. In vitro stimulation of isolated catfish ovarian follicles with vasotocin (VT) or human chorionic gonadotropin (hCG), which induce oocyte maturation and hydration, elevated the hfaqp1b transcript levels after 6 or 16 h of incubation, respectively. These results suggest that HfAqp1b may play a role during VT- and hCG-induced oocyte hydration in catfish, and that VT may regulate HfAqp1b at the transcriptional and post-translational level in a manner similar to the vasopressin-dependent mammalian AQP2.

journal_name

Gen Comp Endocrinol

journal_title

General and comparative endocrinology

authors

Chaube R,Chauvigné F,Tingaud-Sequeira A,Joy KP,Acharjee A,Singh V,Cerdà J

doi

10.1016/j.ygcen.2010.10.002

subject

Has Abstract

pub_date

2011-01-01 00:00:00

pages

162-71

issue

eissn

0016-6480

issn

1095-6840

pii

S0016-6480(10)00348-5

journal_volume

170

pub_type

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Molecular and functional characterization of catfish (Heteropneustes fossilis) aquaporin-1b: changes in expression during ovarian development and hormone-induced follicular maturation.