Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates the expression of PACAP in cultured tilapia astrocytes.
Neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic hormone that is involved in numerous physiologic functions. The present study examines the presence and the functional significance of PACAP and its receptor in the brain and astrocytes of tilapia (Oreochromis mossambicus). This is the first demonstration of the full-length nucleotide sequence of tPACAP gene in tilapia pituitary, brain, and cultured astrocytes. Two cDNA variants of the growth hormone-releasing hormone (GHRH)-PACAP gene were identified in tilapia pituitary, brain, and cultured astrocytes as a result of exon skipping with a long form (271 bp) encoding both tPACAP(38) and tGHRH and a short form (166 bp) encoding only tPACAP(38). The short form was found to be more abundant in astrocytes. Addition of ovine PACAP(38) (1 nM) to cultured astrocytes significantly stimulated the expression of tPACAP(38) at 4 hrs, but the effect dropped after 8 hrs of treatment. By contrast, the expression of PACAP type I receptor (PAC(1)-R) mRNA in the astrocytes was not responsive to PACAP(38) treatment. The tPACAP(38) expression also was activated by the cAMP analog, dibutyryl-cAMP, in a dose-dependent manner. Adding high salinity (170 mM NaCl, 500 mOsm/kg osmolarity) to cultured medium substantially increased astroglial tPACAP(38) expression over 4 hrs to a level that was maintained for 16 hrs. This observation was not found when mannitol (270 mM) was supplemented as an osmolarity-enhancing agent (500 mOsm/ kg). Taken together, tPACAP expression in tilapia astrocytes was well regulated by exogenous PACAP, cAMP, and salinity and might be involved in the adaptation to high salinity when the fish is in a seawater environment.
Chi-Wei
Lo
L
Institute of Biotechnology, National Dong Hwa University, Hualien 974, Taiwan.
Chang
Shang-Lin
SL
Weng
Ching-Feng
CF
D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001483:Base Sequence; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D004247:DNA; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics / Q000494:pharmacology*; D012756:Sheep; D017210:Tilapia
D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D003994:Bucladesine; D004247:DNA