A preprogalanin cDNA from the turtle pituitary and regulation of its gene expression

Abstract

Galanin is a hormone 29 or 30 amino acids (aa) long that is widely distributed within the body and exerts numerous biological effects in vertebrates. To fully understand its physiological roles in reptiles, we analyzed preprogalanin cDNA structure and expression in the turtle pituitary. Using the Chinese soft-shell turtle (Pelodiscus sinensis order Testudines), we obtained a 672-base pair (bp) cDNA containing a 99-bp 5Ј-untranslated region, a 324-bp preprogalanin coding region, and a 249-bp 3Ј-untranslated region. The open-reading frame encoded a 108-aa preprogalanin protein with a putative 23-aa signal sequence at the NH 2 terminus. Based on the location of putative Lys-Arg dibasic cleavage sites and an amidation signal of Gly-Lys-Arg, we propose that turtle preprogalanin is processed to yield a 29-aa galanin peptide with Gly 1 and Thr 29 substitutions and a COOH-terminal amidation. Sequence comparison revealed that turtle preprogalanin and galanin-29 had 48 -81% and 76 -96% aa identities with those of other vertebrates, respectively, suggesting their conservative nature. Expression of the turtle galanin gene was detected in the pituitary, brain, hypothalamus, stomach, liver, pancreas, testes, ovaries, and intestines, but not in the adipose or muscle tissues, suggesting tissue-dependent differences. An in vitro study that used pituitary tissue culture indicated that treatment with 17␤-estradiol, testosterone, or gonadotropin-releasing hormone resulted in increased galanin mRNA expression with dose-or time-dependent differences, whereas leptin and neuropeptide Y reduced galanin mRNA levels. These results suggest a hormone-dependent effect on hypophyseal galanin mRNA expression.estrogen; androgen; gonadotropin-releasing hormone; neuropeptide Y; leptin GALANIN, a 29-amino acid (aa) hormone, was first isolated from porcine intestine and used to stimulate contractions of rat smooth muscle and to cause hyperglycemia in dogs (52). Since its discovery, galanin has also been found to exhibit numerous actions in vertebrates. For example, it induces feeding and the release of pituitary hormones [i.e., luteinizing hormone (LH) and growth hormone (GH)], decreases circulating levels of oxytocin, plays an antinociceptive role in the spinal cord, is involved in gastrointestinal motility and autonomic function, inhibits memory and learning, and promotes smooth muscle contractions (12). Moreover, clinical investigations have shown that galanin levels and galanin receptors are related to human disorders, such as Alzheimer disease and obesity (12). In reptiles, galanin can control gastrointestinal blood flow (24) and female oviposition (29). Although its mechanism of action in these reptilian physiological processes remains unknown, galanin in mammals reportedly operates via G i /G 0 -proteincoupled receptors involving effector systems such as K ϩ channels, Ca 2ϩ channels, and adenylate cyclase (3). In mice and humans, the galanin gene contains six exons and five introns (14, 26), and its mRNA consists of 398 -989 base pairs (bp),...

Galanin is an autocrine myelin and oligodendrocyte trophic signal induced by leukemia inhibitory factor

“…In duplicate experiments, an anti‐galanin antibody detected a strong LIF‐induced increase in a band at approximately14 kD (Fig. a), corresponding to the reported size of secreted preprogalanin (Lang et al, ; Yu et al, ). We also exposed high‐density cultures of the oligodendroglial cell line, CG4, to either LIF (100 ng/mL) or “no additional factor” for 48 h (all in the presence of insulin) and once again identified a 14 kD band by Western blot analysis that was significantly induced by LIF.…”