Is crustacean hyperglycaemic hormone precursor-related peptide a circulating neurohormone in crabs?

Abstract

Sites of synthesis and release patterns of crustacean hyperglycaemic hormone precursor-related peptide (CPRP) were investigated with those of crustacean hyperglycaemic hormone (cHH), in order to determine whether this precursor-related peptide satisfies certain criteria necessary for its definition as a secretable, circulating hormone. Using the edible crab, Cancer pagurus, sites of CPRP synthesis were determined by immunohistochemistry and release patterns of both peptides were determined in vivo and in vitro by radioimmunoassay of haemolymph and eyestalk superfusates. Both peptides were co-released from sinus glands (SGs) following potassium-evoked depolarization of isolated eyestalk preparations. However, stress-evoked in vivo release resulted in apparent non-stoichiometric circulating peptide profiles. This phenomenon is explained by notable differences in clearance rates of the peptides in haemolymph. In contrast to cHH, CPRP is very slowly degraded in vivo. Although CPRP is clearly a circulating peptide, whose release is concomitant with that of cHH, physiologically pertinent roles for this molecule remain to be discovered.

Identification and developmental expression of mRNAs encoding crustacean cardioactive peptide (CCAP) in decapod crustaceans

“…Carcinus sinus gland (SG) and PO express three crustacean hyperglycaemic hormone precursor-related peptide (CPRP) variants (Dircksen et al, 2001), and others (Cancer productus) may express up to four CPRPs, and possibly truncated variants (Fu et al, 2005b). To date no biological activity has been ascribed to these peptides, and for CPRP, in view of its notably long half-life in circulation (Wilcockson et al, 2002), a hormonal role seems unlikely. Additionally, for the CCAP precursor, it should be noted that there are few similarities in sequence of the putative peptides identified so far when insects and crustaceans are compared, and none of these bear C-terminal amidation sites characteristic of the majority of secreted neuropeptides.…”

Serotonin, but not dopamine, controls stress response and anxiety-like behavior in crayfish, Procambarus clarkii.

“…Moreover, the link between 5-HT and glucose has been previously highlighted using 5-HT antagonists, which are able to block the increase in glucose concentrations in crayfish (Lee et al, 2000). Various stressors elicit the release of CHHs and the subsequent increase in blood glucose in crustaceans, such as hypoxia and emersion, disease, thermal stress, heavy metals exposure or social interactions (Webster, 1996;Chang et al, 1998;Stentiford et al, 2001;Wilcockson et al, 2002;Lorenzon et al, 2004;Elwood, 2011;Aquiloni et al, 2012). Thus, it would be interesting to further study the consequences of such stressors in terms of ALB and of 5-HT accumulation in the brain.…”

Role of biogenic amines and cHH in the crustacean hyperglycemic stress response

“…(Stentiford et al, 2001). Finally, increased water temperature induced an increment in blood cHH in C. pagurus and the crayfish Procambarus clarkii (Wilcockson et al, 2002;Zou et al, 2003).…”