Activation of VIP/PACAP type 2 receptor by the peptide histidine isoleucine in astrocytes influences GLAST-mediated glutamate uptake.
Considering the putative neuroprotective role of the vasoactive intestinal peptide (VIP) and the pituitary adenylyl cyclase-activating polypeptide (PACAP), we investigated the acute modulation of glial glutamate uptake by the structurally related peptide histidine isoleucine (PHI). Using cultures of cortical astrocytes, we demonstrated that a 6 min treatment with 1 micromol/L PHI strongly increased the d-[3H]-aspartate uptake velocity from 24.3 +/- 1.9 to 46.8 +/- 3.5 nmol/mg prot/min. This effect was found to reflect an increase in the activity of the GLAST, the predominant functional glutamate transporter in these cultures. The combination of protein kinase A and C inhibitors was effective in blocking the effect of PHI and the use of peptide antagonists contributed to demonstrate the implication of the VIP/PACAP type 2 receptor (VPAC(2)). Accordingly, G-protein activation measures and gene reporter assays revealed the expression of functional PHI-sensitive receptors in cultured astrocytes. Biotinylation/immunoblotting studies indicated that PHI significantly increased the cell surface expression of the GLAST (by 34.24 +/- 8.74 and 43.00 +/- 6.36%, when considering the 72 and 55 kDa immunoreactive proteins, respectively). Such cross-talk between PHI and glutamate transmission systems in glial cells opens attractive perspectives in neuropharmacology.
Goursaud
Stéphanie
S
Laboratoire de Pharmacologie Expérimentale, Université Catholique de Louvain, Av. Hippocrate 54.10, 1200 Brussels, Belgium.
Maloteaux
Jean-Marie
JM
Hermans
Emmanuel
E
D027322:Amino Acid Transport System X-AG / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D010451:Peptide PHI / Q000494:pharmacology* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D013552:Swine
D027322:Amino Acid Transport System X-AG; D010451:Peptide PHI; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D018698:Glutamic Acid