Formation and sequence analysis of secretoneurin, a neuropeptide derived from secretogranin II, in mammalian, bird, reptile, amphibian and ﬁsh brains Bernd Leitner a , Clemens Schneitler a , Helmut Klocker b , Walter Volknandt c , Herbert Zimmermann c , Hans Winkler a , Reiner Fischer-Colbrie a, * a Department of Pharmacology, University of Innsbruck, Peter-Mayr-Strasse 1a, A 6020 Innsbruck, Austria b Department of Urology, University of Innsbruck, Innsbruck, Austria c Department of Zoology, Biocenter, University of Frankfurt, Frankfurt, Germany Received 20 March 1998; received in revised form 17 April 1998; accepted 17 April 1998 Abstract Secretoneurin is a recently-characterized neuropeptide derived from secretogranin II, a protein belonging to the class of chromogranins. We investigated the phylogeny of this peptide by immunoblotting and gel-ﬁltration high performance liquid chromatography followed by radioimmunoassay of brain extracts of various species including chicken, lizard, frog and ﬁsh. In addition the amino acid sequence of secretoneurin from pig, hamster, rabbit, guinea-pig and chicken was established by reverse transcriptase polymerase chain reaction. Secretoneurin is strongly conserved during evolution, it is not only expressed in various mammalian species but found also in the brain of birds, reptiles, amphibians and ﬁsh. In all these species a signiﬁcant or near complete processing of secretogranin II to secretoneurin was observed. These data provide signiﬁcant evidence for the neu- ropeptide nature of the novel functional peptide.  1998 Elsevier Science Ireland Ltd. All rights reserved Keywords: Chromogranin; Phylogeny; Amino acid sequence; Adrenal medulla; Brain Secretoneurin (SN, [15]) is a novel functional peptide derived from secretogranin II [5], a protein belonging to the class of chromogranins [11,31]. It is generated in vivo from secretogranin II by the subtilisin-like prohormone con- vertases PC1/3 and PC2 [3,9,18]. SN is found in the large dense core secretory vesicles of a variety of neurons and endocrine cells [15] and released from them in a calcium dependent manner [29]. In the central nervous system SN is speciﬁcally distributed in phylogenetically older regions of the brain [19]. In the periphery, SN is expressed in sympa- thetic and sensory nerves as well as endocrine tissues like the adrenal medulla, pituitary or the endocrine cells of the gastrointestinal tract [4,15,16,27]. Several biological effects have been attributed to SN. In the central nervous system SN induced dopamine release from rat striatal slices [23] as well as dopamine [1] and dynorphin B [32] release from freely-moving rats in vivo in a microdialysis study. SN might also play a role in macrophage recruitment into inﬂammatory lesions of the central nervous system [28]. In the periphery, SN exerts a potent chemotactic effect towards smooth muscle, endothelial and immune cells. SN inhibits growth of aortic and pulmonary artery endothelial cells in vitro at concentrations of 10 nM and stimulates the migration of these cells [14]. SN exerts a chemotactic action towards skin ﬁbroblasts [13] and smooth aortic muscle cells [12]. It triggers selective migration of human monocytes in vitro and in vivo [22]. In contrast to other sensory neuropep- tides, SN chemotaxis is highly speciﬁc for monocytes, SN does not attract granulocytes or other mononuclear cells like lymphocytes [26]. Recently speciﬁc high-afﬁnity binding sites for SN were identiﬁed on a human monocytic cell line [25]. Cloning of its precursor secretogranin II established the amino acid sequence of SN from human [7], rat [8], mouse [24], ox [6] and frog [2,10]. These studies indicated that SN Neuroscience Letters 248 (1998) 105–108 0304-3940/98/$19.00  1998 Elsevier Science Ireland Ltd. All rights reserved PII S0304-3940(98)00345-0 * Corresponding author. Tel. +43 512 5073720; fax: +43 512 5072868; e-mail: ﬁscher-colbrie@uibk.ac.at