PACAP system evolution and its role in melanophore function in teleost fish skin.
Pituitary adenylate cyclase-activating polypeptide (PACAP) administered to tilapia melanophores ex-vivo causes significant pigment aggregation and this is a newly identified function for this peptide in fish. The G-protein coupled receptors (GPCRs), adcyap1r1a (encoding Pac1a) and vipr2a (encoding Vpac2a), are the only receptors in melanophores with appreciable levels of expression and are significantly (p < 0.05) down-regulated in the absence of light. Vpac2a is activated exclusively by peptide histidine isoleucine (PHI), which suggests that Pac1a mediates the melanin aggregating effect of PACAP on melanophores. Paradoxically activation of Pac1a with PACAP caused a rise in cAMP, which in fish melanophores is associated with melanin dispersion. We hypothesise that the duplicate adcyap1ra and vipr2a genes in teleosts have acquired a specific role in skin and that the melanin aggregating effect of PACAP results from the interaction of Pac1a with Ramp that attenuates cAMP-dependent PKA activity and favours the Ca(2+)/Calmodulin dependent pathway.
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal. Electronic address: jccardo@ualg.pt.
João C R
JC
Cardoso
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Rute C
RC
Félix
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Rute S T
RS
Martins
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Marlene
M
Trindade
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Vera G
VG
Fonseca
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Juan
J
Fuentes
Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Deborah M
DM
Power
D000818:Animals; D005075:Biological Evolution; D016208:Databases, Factual; D008547:Melanophores / Q000378:metabolism*; D010802:Phylogeny; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*; D017210:Tilapia
D051219:Pituitary Adenylate Cyclase-Activating Polypeptide
Family B GPCRs; Functional divergence; Gene duplication; PACAP and receptors; RAMPs; Teleost skin melanophores