Molecular cloning, sequence and expression of follicle-stimulating hormone receptor in the lizard Podarcis sicula

Role of gonadotropin and Leydig cell-secreted factors in the control of testicular macrophage activities in the wall lizard Hemidactylus flaviviridis

The present in vitro study for the first time demonstrates the endocrine and paracrine control of testicular macrophage activities in ectodermic vertebrates. Follicle-stimulating hormone (FSH) increased phagocytosis and superoxide production by macrophages. In regard to paracrine control, non-activated Leydig cell-conditioned medium (LCCM) decreased both the activities, whereas FSH-preactivated LCCM had differential effects: inhibitory on phagocytosis and stimulatory on superoxide production. However, FSH-activated LCCM, in addition to superoxide production, also enhanced phagocytosis. After heat inactivation, FSH-activated LCCM inhibited both the activities. Addition of FSH resulted in stimulation of phagocytosis, while partially restored the superoxide production. It can be speculated that androgen in heat-inactivated FSH-activated LCCM, in the presence of FSH, instead of inhibitory had stimulatory effect on phagocytosis, but remained inhibitory to superoxide production. Further, FSH-induced Leydig cell-secreted non-steroidal heat-labile factors appear to have stimulatory effect on superoxide production. This was corroborated by experiments with dihydrotestosterone in presence/absence of FSH.

Molecular cloning, sequence analysis and expression of the snake follicle-stimulating hormone receptor

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) control gonadal function in mammalian and many non-mammalian vertebrates through the interaction with their receptors, FSHR and LHR. Although the same is true for some reptilian species, in Squamata (lizards and snakes) there is no definitive evidence for the presence of either two distinct gonadotropins or two distinct gonadotropin receptors. Our aim was to characterize the gonadotropin receptor(s) of the Bothrops jararaca snake. Using a cDNA library from snake testis and amplification of the 5'-cDNA ending, we cloned a cDNA related to FSHR. Attempts to clone a cDNA more closely related to LHR were unsuccessful. Expression of FSHR mRNA was restricted to gonadal tissues. The snake FSHR is a G protein-coupled receptor with 673 amino acids, and the aminoterminal domain with 346 amino acids consists of a nine leucine-rich repeat-containing subdomain (LRR) flanked by two cysteine-rich subdomains. The beta-strands in the LRR are conserved with exception of the third, a region that may be important for FSH binding. In contrast with mammalian, avian and amphibian FSHRs, the snake FSHR presents amino acid deletions in the carboxyterminal region of the extracellular domain which are also seen in fish and lizard FSHRs. cAMP assays with the recombinant protein transiently expressed in HEK-293 cells showed that the snake FSHR is more sensitive to human FSH (hFSH) than to human chorionic gonadotropin. Phylogenetic analysis indicated that the squamate FSHRs group separately from mammalian FSHRs. Our data are consistent with the apparently unique gonadotropin-receptor system in Squamata reptilian subgroup. Knowledge about the snake FSHR structure may help identify structural determinants for receptor function.

Relationship between adenylate cyclase sensitivity to follitropin and FSH receptor mRNA expression in the ovary of the lizard Podarcis sicula

In mammals, gonadal functions are regulated by two pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), that interact with gonadal membrane receptors to activate adenylate cyclase. In comparison to mammalian systems, in squamate reptiles a reduced amount of information exists on gonadotropins and their related receptors. This study is aimed at clarifying if, in the lizard Podarcis sicula, the ovarian sensitivity to FSH is correlated to the reproductive cycle and to the expression of membrane receptors involved in the hormone recognition. The results demonstrate that the ovarian adenylate cyclase responsiveness to FSH parallels ovarian functions, being maximal during the ovulatory period. The ovarian sensitivity to FSH is also related to oocyte growth and vitellogenesis. Northern blot analyses reveal that the FSH receptor mRNA is maximally expressed in vitellogenic oocytes during the reproductive period. These results suggest that, in lizard ovary, hormone activation of adenylate cyclase is mediated by de novo synthesis of receptors specifically involved in FSH recognition. In lizards treated in vivo with FSH during the pre-ovulatory period, adenylate cyclase becomes refractory to further FSH stimulation 2 hr after treatment, but sensitivity to the hormone is restored after 2 weeks. Nevertheless, while the restored level of activity never exceeds that observed during the nonreproductive period, the expression level of FSH receptor mRNAs is significantly enhanced in these animals. These results suggest that in lizard the processes that regulate ovarian growth, vitellogenesis, and ovulation are controlled by a complex network of signals including gonadotropin, FSH receptor expression, and adenylate cyclase.