Cloning and functional characterization of a testicular TSH receptor cDNA from the African catfish (Clarias gariepinus)

Abstract

A cDNA encoding a putative thyroid-stimulating hormone receptor (cfTSH-R) was cloned from the testis of the African catfish (Clarias gariepinus). The cfTSH-R showed the highest amino acid sequence identity with the TSH-Rs of other fish species. In addition, an insertion of approximately 50 amino acids, specific for the TSH-R subfamily, was also present in the carboxy terminus of the amino-terminal extracellular domain of the cfTSH-R. Next to the testis and thyroid follicles, abundant cfTSH-R expression was detected in cerebellum, brain, ovary, seminal vesicles and pituitary, while weaker expression was found in muscle, stomach, intestine, head-kidney, liver, kidney and heart. HEK-T 293 cells, transiently expressing the cfTSH-R, significantly increased intracellular cAMP levels in response to human TSH. Catfish LH, human choriogonadotropin and human FSH were also able to induce this cfTSH-R-mediated response, although with considerably lower efficiency than human TSH. These results indicated that a functional cfTSH-R had been cloned from the testis of African catfish.

Thyroid hormone regulation of mRNAs encoding thyrotropin β-subunit, glycoprotein α-subunit, and thyroid hormone receptors α and β in brain, pituitary gland, liver, and gonads of an adult teleost, Pimephales promelas

“…We also observed that variation in testis tshb transcript abundance was associated with progression of spermatogenesis, with higher tshb mRNA levels in testes with a greater proportion of mature spermatozoa. Receptors for Tsh have recently been identified in the testicular tissues of several species of teleost fishes, and transcripts for the receptor appear to be localized to the gametes in at least one of these species (Kumar et al 2000, Goto-Kazeto et al 2003, Rahman et al 2003, Vischer & Bogerd 2003, Rocha et al 2007. Transcripts for tshb have also been shown by RT-PCR and in situ hybridization to be present in the testis of another adult teleost: the red-spotted grouper, Epinephelus akaara (Wang et al 2004).…”

Cloning, characterization, expression, and feeding response of thyrotropin receptor in largemouth bass (Micropterus salmoides)

“…It has been reported that four glycosylation sites are necessary for expression and biologic activity in human TSHR, regardless of location. In contrast, the number of potential N-linked glycosylation sites in the extracellular domain of TSHR was found to be three for C. gariepinus (Vischer and Bogerd, 2003), I. punctatus (Goto-Kazeto et al, 2003), and O. rhodurus (Oba et al, 2000). The relationship between the functionality and the three potential N-linked glycosylation sites in teleosts is still not clear.…”

“…In largemouth bass, three of the identified sites, corresponded to NIS (residues 77-79), , and NLT (residues 302-304) of TSHR, confirming that these are highly conserved in teleosts. The first conserved glycosylation site is unique to TSHRs, whereas the other two are also found in other members of the glycoprotein hormone receptor family (Vischer and Bogerd, 2003). It has been reported that four glycosylation sites are necessary for expression and biologic activity in human TSHR, regardless of location.…”

“…Receptors in this subfamily are distinguished by a very large extracellular domain containing multiple leucine-rich repeat motifs (Kumar et al, 2000). Once bound by TSH, the TSHR initiates a dual intracellular signaling cascade, including adenylate cyclase, protein kinase A, phospholipase C, and calcium pathways, which is necessary for the synthesis, storage, and secretion of T4 in the thyroid follicles (Ji et al, 1998;Vischer and Bogerd, 2003). The primarily T4 released from the thyroid follicles is then converted to T3 in most tissues.…”

“…The complete cDNA sequence of TSHR has been cloned in some fishes including Oncorhynchus rhodurus (Oba et al, 2000), Morone saxatilis (Kumar et al, 2000), Clarias gariepinus (Vischer and Bogerd, 2003), Ictalurus punctatus (Goto-Kazeto et al, 2003), Dicentrarchus labrax (Rocha et al, 2007), and Solea senegalensis (Ponce et al, 2010). These sequences have allowed us a partial understanding of the molecular structure and functions of TSHR in teleost fish.…”