Molecular characterization of three forms of putative membrane-bound progestin receptors and their tissue-distribution in channel catfish, Ictalurus punctatus

Abstract

Membrane-bound progestin receptors (mPR) were recently cloned and characterized as a new class of steroid receptors that transduce cell-signals through alteration of MAP kinase-and cAMP-dependent pathways. To further develop our understanding of this new class of steroid receptors, we characterized the cDNAs and genes of the , and forms of the channel catfish mPRs (IpmPR). The predicted and proteins have 49% sequence identity, whereas they only have 30% and 27% identities, respectively, with the form. Furthermore, IpmPR and IpmPR genes have similar structures featuring intronless coding regions, while IpmPR gene is composed of 8 exons and 7 introns. The 58-flanking region of each IpmPR gene differs, but each contains putative transcriptional regulatory elements of factors known to influence reproductive physiology and endocrine disruption, for example, responsive elements for cAMP and steroids and the recognition sites for steroidogenic factor-1 and for the aryl hydrocarbon receptor. The IpmPR gene was detected in all the tissues tested with relatively greater expression in brain, pituitary, muscle and testis. The expression of IpmPR was much lower than that of IpmPR and the transcript was predominantly observed in brain, pituitary, ovary and testis. In contrast, the IpmPR transcript was mainly detected in gill, ventral aorta, intestine, and trunk kidney. In conclusion, all the structural features of the IpmPRs strongly suggest that the closely related and forms are distantly related to the form. Additionally, regulatory features of the 58-flanking regions and the differences in tissue-specific expression of each IpmPR gene suggest that they are involved in different endocrine functions in catfish.

New Insight into Progesterone-dependent Signalization

“…In catfish, amino acid homology among mPR subtypes, i.e. between α and β, is 50%, whereas among γ and the remaining two is less than 30% [44].…”

“…Three subfamilies have been distinguished within the PAQR family on the basis of phylogenetic analysis: receptors related to adiponectin, membrane receptors for progestins, and receptors associated with hemolysin III. Generally, 11 proteins typical for mammals (PAQR I-XI), as well as hemolysin III derived from Bacillus cereus (HLYIII), YOLOOLC and Sacharomyces cerevisiae proteins have been included [42,44]. Adiponectin receptors: PAQR I, II, III, IV, YOLOO2C and other yeast proteins, transmembrane adiponectin receptors 1 and 2 (adipoRs) derived from Eubacteria, are all involved in lipid homeostasis regulation (especially fatty acids), as well as phosphate and zinc metabolism.…”

“…Human gene for mPRα consists of three exons separated by two introns, gene for mPRβ has two exons and one additional intron in comparison to mPRα, while the gene for mPRγ is composed of eight exons and seven introns [5,44]. 5'-end is deprived of typical TATA sequence (TATA box); the proximal region is abundant in GC pairs.…”

“…Transcripts of mPRα have been identified in the ovaries (corpus luteum), testes, placenta, amnion, chorion, uterus (myometrium and endometrium), mammary gland, brain (hypothalamus, hypophysis), heart, intestines, liver, spleen, skeletal muscles, adrenal glands, and lungs [26,35]. Transcripts of mPRβ have been identified in the brain, hypophysis, ovaries and testes, and mPRγ -in the abdominal aorta, and intestines [31,35,44]. A significant level of the expression of all three subtypes has been demonstrated only in kidneys [35].…”

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…In mammals, the former orphan receptor GPR30 was characterized as an E2 membrane receptor, and is also called G-protein coupled estrogen receptor GPER (Filardo and Thomas, 2005;Filardo et al, 2007; for review see Prossnitz and Maggiolini, 2009). Two membrane GPERs have recently been observed in most teleosts including in the eel, likely resulting from teleost 3R (Lafont et al, in press).…”