Pituitary adenylate cyclase activating polypeptide (PACAP) stimulates mitogen-activated protein kinase (MAPK) in cultured rat astrocytes.
Astrocytes, a subtype of glial cells, have been demonstrated to have an abundant number of receptors for pituitary adenylate cyclase activating polypeptide (PACAP), a neuropeptide of the VIP/secretin family which stimulates cAMP accumulation 1000 times more potent than VIP in astrocytes. PACAP is reported to stimulate the proliferation of astrocytes at low concentrations at which it does not yet stimulate the cAMP accumulation. In the present study, we examined the effect of PACAP on the activation of mitogen-activated protein kinase (MAPK), one of the important intracellular signals for the proliferation, and compared it with that of epidermal growth factor (EGF). To investigate the activation of MAPK, we focused on ERK2, one of MAPK, in cultured rat astrocytes. The activation of ERK2 was determined by immunoblotting and measurement of the activity in terms of the phosphorylating activity of immunoprecipitates with MAPK antibody on myelin basic protein. One pM of PACAP38 temporarily activated ERK2 at 10 min. In contrast, EGF activated ERK2 from 10 min to 60 min continuously. As for the dose-response effect, PACAP stimulated ERK2 at as low a concentration as 10-14 M and peaked at 10-12 M. Thereafter, its activating effect gradually decreased at 10-10 M and returned to the basal level at 10-8 M, forming a bell-shaped dose-dependency. Neither an inhibitor of PKA (H89) nor inhibitors of PKC (staurosporine and calphostin C) had any effect on the ERK2 activation induced by 1 pM PACAP38. Dibutyryl cAMP suppressed ERK2 activity in a dose-dependent manner. These data clearly demonstrated that PACAP stimulates MAPK in both a PKA- and a PKC-independent manner in cultured rat astrocytes.
Moroo
I
I
Department of Neurology, Chiba University School of Medicine, Chiba, Japan.
Tatsuno
I
I
Uchida
D
D
Tanaka
T
T
Saito
J
J
Saito
Y
Y
Hirai
A
A
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D003994:Bucladesine / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007546:Isoquinolines / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D019950:Mitogen-Activated Protein Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009479:Neuropeptides / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011247:Pregnancy; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides; D048051:p38 Mitogen-Activated Protein Kinases
C495403:Adcyap1 protein, rat; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D013449:Sulfonamides; D003994:Bucladesine; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide