Purification and characterization of peptides with corticotropin-releasing factor activity from porcine hypothalami.

Abstract

Ten polypeptides that stimulated the release of corticotropin from superfused rat pituitary cells and that are structurally related to porcine corticotropin-releasing factor were isolated from porcine hypothalami. The purification was carried out by gel ifitration followed by reversed-phase HPLC using trifluoroacetic acid or heptafluorobutyric acid as the ion-pairing agent in water/acetonitrile solvent systems. The purified peptides were homogeneous by chromatography and by sequence analysis. One major polypeptide was characterized. Its structure is -H-Ser-Glu-Glu-Pro-Pro-fle-Ser-Leu--Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Met--Ala-Arg-Ala-Glu-Gln-Leu-Aa-Gln-Gln-Ala-His-Ser-Asn-Arg- This 41-amino acid sequence is thought to represent porcine corticotropin-releasing factor. Based on automated gas-phase sequencing of the intact and CNBr-cleaved peptides, amino acid analysis, and carboxypeptidase Y digestion, the other nine polypeptides were found to be structurally similar to this 41-amino acid sequence. Modifications of this structure include deamidation of glutamine at position 26 or 29, oxidation of methionine at positions 21 and/or 38, a blocked N terminus, and deletion of phenylalanine amide at the C terminus. Eight of these nine modified peptides retained significant corticotropin-releasing factor activity as shown by the stimulation of corticotropin release from superfused rat and pig pituitary cells. Some of these peptides may be present in pig hypothalami, while the others could have been produced during the isolation.Vale et al. (1, 2) purified and determined the amino acid sequence of ovine corticotropin-releasing factor (CRF) and carried out its synthesis (1, 3). This work was followed by the isolation and identification of rat CRF (4, 5), deduction of the structure of human CRF from the cDNA sequence of its gene (6), and characterization of caprine and bovine CRF (7,8). We have reported the isolation and structure of porcine CRF (9). Here we present the purification and structural characterization of several other peptides with CRF activity from extracts of porcine hypothalami. MATERIALS AND METHODSPurification. A total of 470,000 porcine hypothalami were dissected, defatted, and extracted with 2 M acetic acid as reported (10, 11). The extracts were purified by preparative gel filtration on 12). Ten grams of Sephadex fractions 557-656 with Rf = 0.82-0.7 (see figure 1 of ref. 12), from 16,600 hypothalami, was dissolved in 1 liter of buffer A [0.1% trifluoroacetic acid (F3CCOOH) in water] containing 0.2% 2-mercaptoethanol and centrifuged at 17,500 x g for 20 min. The supernatant was pumped onto a 2.5 x 50 cm glass column, packed with SynChroprep RP-P packing material (SynChrom, Linden, IN), and eluted as described (9). This step was repeated 10 times; thus a total of 100 g of material from 166,000 hypothalami was processed.For both the semipreparative and analytical HPLC separations, prepacked Vydac 218TP5 reversed-phase columns were used. In the first three purification steps, the samp...

Corticotropin-Releasing Factor-Like Immunoreactivity, Arginine Vasopressin-Like Immunoreactivity and ACTH-Releasing Bioactivity in Hypothalamic Tissue from Fetal and Neonatal Sheep

“…Whether such polymorphism also occurs in the fetal sheep remains, however, to be eluci dated. On the other hand, an increase in the hypothalamic content of another corticotropin-releasing factor [II,15] around 143 days of gestation cannot be disregarded.…”

“…However, the regulation of synthesis and secretion of ACTH by the ovine fetal pituitary remains poorly understood [5], In adult animals, the multi factorial nature of corticotrophin-releasing activity has been clearly established [11,15]. In the sheep, recent in vivo (13,14] and in vitro [3,6] studies have shown that 0CRF1-41 and arginine vasopressin (AVP) are the most potent hypothala mic factors (among those tested), able to stimulate the re lease of both immunoreactive and bioactive ACTH-like acti vity from pituitary cells between 63 days of intrauterine life and 150 days postpartum.…”

Eferências do núcleo lateral superior da oliva no rato (rattus norvegicus).

“…Além destes, o CRF também foi isolado e caracterizado em outras espécies como bovinos , caprinos , porcinos (PATTHY et al, 1985), anfíbios (Xenopus) (STENZEL-POORE et al, 1992) e peixes (Sucker -Catostomus commersoni) (MORLEY et al, 1991).…”

“…A Urotensina I (Uro-I), peptídeo composto de 41 aminoácidos, foi isolada a partir do sistema magnocelular neurossecretor, chamado urófise, localizado na extremidade caudal da medula espinhal de peixes teleósteos (Catostomus commersoni) o qual parece apresentar uma estrutura anatomicamente análoga à neuro-hipófise humana (hipófise posterior) 1985 a, b;BERN et al, 1985;MINNITI et al, 1989;BARSYTE et al, 1999). Este peptídeo, sintetizado em 1982 por Lederis e colaboradores e localizado por métodos imunoistoquímicos no sistema neurosecretor caudal de diversas espécies de teleósteos (YAMADA et al, 1986), apresenta 50% de homologia estrutural com o CRF 1985b).…”

Distribuição dos neurônios e campos terminais que expressam a urocortina 3 no sistema nervoso central de primata não-humano (Cebus apella).

“…A descrição do CRF de rato (CRFr) e humano (CRFh) demonstrou a grande homologia existente entre a estrutura destes e a do CRFo . O CRF também foi isolado e caracterizado em bovinos , caprinos , porcinos (Patthy et al, 1986), anfíbios (Stenzel-Poore et al, 1992) e peixes (Morley et al, 1991).…”