Involvement of calcitonin and its receptor in the control of calcium-regulating genes and calcium homeostasis in zebrafish (Danio rerio)

Abstract

Calcitonin (CT) is one of the hormones involved in vertebrate calcium regulation. It has been proposed to act as a hypocalcemic factor, but the regulatory pathways remain to be clarified. We investigated the CT/calcitonin gene-related peptide (CGRP) family in zebrafish and its potential involvement in calcium homeostasis. We identified the presence of four receptors: CTR, CRLR1, CRLR2, and CRLR3. From the phylogenetic analysis, together with the effect observed after CT and CGRP overexpression, we concluded that CTR appears to be a CT receptor and CRLR1 a CGRP receptor. The distribution of these two receptors shows a major presence in the central nervous system and in tissues involved in ionoregulation. Zebrafish embryos kept in high-Ca 2þ -concentration medium showed upregulation of CT and CTR expression and downregulation of the epithelial calcium channel (ECaC). Embryos injected with CT morpholino (CALC MO) incubated in high-Ca 2þ medium, showed downregulation of CTR together with upregulation on ECaC mRNA expression. In contrast, overexpression of CT cRNA induced the downregulation of ECaC mRNA synthesis, concomitant with the downregulation in the calcium content after 30 hours postfertilization. At 4 days postfertilization, CT cRNA injection induced upregulation of hypercalcemic factors, with subsequent increase in the calcium content. These results suggest that CT acts as a hypocalcemic factor in calcium regulation, probably through inhibition of ECaC synthesis. ß

STC1 interference on calcitonin family of receptors signaling during osteoblastogenesis via adenylate cyclase inhibition

“…The distinct effect of hSTC1 on cAMP levels elicited by hCGRP and hCT peptides may be related with the different capacities that both peptides had on cAMP production in vitro and that hCT was more potent than hCGRP in the HEK293 cell assay. Cross regulation of CT and STC has previously been suggested and an increase of CT peptide production in zebrafish eggs was shown to stimulate the increase expression of STC1 transcript resulting in a decrease of total calcium (Lafont et al, 2011). The fish data may indicate that the action of CT and STC1 may be coordinated in tetrapods and that STC1 may inhibit the role of CT in vivo, as suggested by our cAMP in vitro assays.…”

“…Based on the fact that calcitonin family peptides and STC1 act on bone metabolism, we hypothesize that their signaling pathways may interact with each other. Recently in the zebrafish embryo model, it was demonstrated that overproduction of CT peptide increased by 3-fold the expression of STC1 suggesting a feedback mechanism between the two hormones (Lafont et al, 2011). Thus, the present study was designed to better elucidate the role of STC1 in human bone formation/remodeling by investigating the potential role of STC1 on CGRP signaling during the differentiation of osteoblast, and to determine whether STC1 modulates CTR and the CGRP functional receptor.…”

Inhibition of calcium uptake during hypoxia in developing zebrafish, Danio rerio, is mediated by hypoxia-inducible factor

“…In the present study, we also evaluated the effects of hypoxia on two hypocalcaemic hormones, stanniocalcin-1 (stc-1) and calcitonin (ct). These hormones were shown to inhibit Ca 2+ uptake by decreasing the expression of ecac in larval zebrafish (Lafont et al, 2011;Tseng et al, 2009). Both stc-1 and ct were found to be expressed before 1 dpf, and continued to be expressed over development (Lafont et al, 2011;Tseng et al, 2009).…”

“…These hormones were shown to inhibit Ca 2+ uptake by decreasing the expression of ecac in larval zebrafish (Lafont et al, 2011;Tseng et al, 2009). Both stc-1 and ct were found to be expressed before 1 dpf, and continued to be expressed over development (Lafont et al, 2011;Tseng et al, 2009). Hypoxic treatment was reported to stimulate STC-1 mRNA and/or protein levels in various mammalian cell lines (Ito et al, 2014;Yeung et al, 2005).…”

A novel function of calcitonin gene-related peptide in body fluid Cl−homeostasis

“…Zebrafish only have one CGRP [17], which is an orthologue of human aCGRP according to NCBI and Ensembl databases. In zebrafish, CT acts through the calcitonin receptor (CTR) as a hypocalcemic factor for body fluid Ca 2þ homeostasis, while CGRP acts through the calcitonin receptor-like receptor 1 (CRLR1) without any effect on Ca 2þ regulation [17]. In mammals, CGRP is known to be involved in the control of cardiovascular functions through acting as a hypotensive factor on heart and blood vessels [18,19].…”