Biochemical Characterisation and Immunohistochemical Localisation of the Secretogranin II‐Derived Peptide EM66 in the Hypothalamus of the Jerboa (Jaculus orientalis): Modulation by Food Deprivation

Abstract

The neuroendocrine protein secretogranin II is the precursor of several neuropeptides, including secretoneurin and a novel 66-amino acid peptide, EM66, the sequence of which has been highly conserved across the vertebrae phylum. The presence of EM66 has been detected in the adult and fetal human adrenal gland, as well as the rat pituitary and adrenal glands. The present study aimed to explore a possible neuroendocrine role of EM66 by analysing its occurrence and distribution within the jerboa hypothalamus, and its potential implication in the control of feeding behaviour. High-performance liquid chromatography analysis of jerboa hypothalamic extracts combined with a radioimmunoassay of EM66 revealed a single peak of immunoreactive material exhibiting the same retention time as recombinant EM66. Immunocytochemical labelling showed that EM66-producing neurones are widely distributed in several hypothalamic regions, including the preoptic area, the suprachiasmatic, supraoptic, parvocellular paraventricular and arcuate nuclei, and the lateral hypothalamus. Food deprivation for 5 days induced a significant increase in the number of EM66-containing neurones within the arcuate nucleus (105% increase) and the parvocellular aspect of the paraventricular nucleus (115% increase), suggesting that EM66 could be involved in the control of feeding behaviour and/or the response to stress associated with fasting. Altogether, these data reveal the physiological plasticity of the EM66 system in the hypothalamus and implicate this novel peptide in the regulation of neuroendocrine functions.

Vasopressin-Containing Neurons of the Hypothalamic Parvocellular Paraventricular Nucleus of the Jerboa: Plasticity Related to Immobilization Stress

“…Cell counts were performed by direct microscopic observation in a blinded fashion. The neuranatomical identification of the hypothalamic structures was based both on the atlas of the rat brain by Paxinos and Watson [34] and data previously described for rats and jerboas [26, 29]. Quantification of VP-immunoreactive cell bodies within the parvocellular PVN of control and stressed jerboas was performed bilaterally on four sections per animal, and an average value was calculated for each animal.…”

“…To face these harsh conditions, jerboas trigger various adaptative neuroendocrine regulations involving different hypothalamic neuropeptides. For instance, in the jerboa arcuate nucleus, food deprivation and hibernation induce an important increase in the expression of neuropeptide Y, which is known to regulate energy expenditure [24, 25], and of a novel neuropeptide, EM66 [26]. The hibernation state characterized by hypothermia is accompanied by a slowing of main vital functions [23].…”

Molecular Cloning, Mapping, and Polymorphism of the Porcine SCG2 gene

“…Additionally, pig SCG2 has nine pairs of dibasic sites that are potential cleavage sites in the posttranslational modifications by endoproteolytic enzymes (Muller et al 1997), which is consistent with those of the other homologs, such as rat (Gerdes et al 1988), human (Gerdes et al 1989), and ox (Fischer-Colbrie et al 1990). Previously, two secretogranin II-derived peptides, SN and EM66, have been identified from human, rat, and jerboa and have been widely studied (Anouar et al 1998;Montero-Hadjadje et al 2003;Boutahricht et al 2005Boutahricht et al , 2007Zhao et al 2006;Guillemot et al 2006), and manserin, another neuropeptide of 40 amino acids from secretogranin II, has also been isolated recently from the rat in the neuroendocrine system (Yajima et al 2004). Putative pig SN, EM66, and manserin were indicated in the present study based on those sequences from human and rat (Anouar et al 1998;Yajima et al 2004).…”

Chromogranins A and B and Secretogranin II as Prohormones for Regulatory Peptides from the Diffuse Neuroendocrine System

“…Moreover, the N-and C-terminal domains of SN have been immunodetected in all insulinpositive cells, most of the glucagon cells, and some of the pancreatic poloypeptide cells while no SgII peptide could be detected in the somatostatin cells (Stridsberg et al 2008). A wide range of biological activities has been assigned to SN (Vaudry and Conlon 1991;Kirchmair et al 1993;Kähler and Fischer-Colbrie 2000) and there are indications of a functional relevance for EM66 in the control of food intake and/or the stress associated with fasting (Boutahricht et al 2005).…”