A lymphocyte-generated fragment of vasoactive intestinal peptide with VPAC1 agonist activity and VPAC2 antagonist effects.
Vasoactive intestinal peptide receptors 1 (VPAC1) and 2 (VPAC2) have been identified in humans. Cell lines expressing only VPAC1 (HT-29) or VPAC2 (Molt-4b) were identified using real-time reverse transcriptase polymerase chain reaction. Vasoactive intestinal peptide (VIP) and related peptides, VIP-6-28, VIP4-28, and VIP10-28, previously isolated from cultures of human leukocytes, were evaluated for their ability to bind to VPAC1 and VPAC2 and to increase the levels of cAMP in HT-29 and Molt-4b cells. VIP bound to membranes of HT-29 colon carcinoma cells and Molt-4b lymphoblasts with high affinity (KD = 1.6 +/- 0.2 and 1.7 +/- 0.9 nM, respectively). VIP4-28 also demonstrated high-affinity binding (KD = 1.7 +/- 0.2 and 1.7 +/- 0.7 nM in HT-29 and Molt-4b, respectively). VIP and VIP4-28 are potent VPAC1 agonists, inducing maximal 200- and 400-fold increases in cAMP, respectively. VIP demonstrated weak VPAC2 agonist activity, inducing a maximal 14-fold increase in cAMP. VIP4-28 had no VPAC2 agonist activity but demonstrated potent VPAC2 antagonist activity. VIP4-28 inhibited VPAC2-mediated increases in cAMP in Molt-4b cells up to 95%, but had no antagonistic effect on VPAC1. Lymphoblasts did not hydrolyze VIP4-28 to a form with VPAC1 antagonist activity. VIP4-28 thus is a lymphocyte-generated VIP fragment with potent agonist activity for VPAC1 and potent antagonist activity for VPAC2.
Depaertment of Pediatrics, University of Iowa City, Iowa City, Iowa 52242, USA.
Monica A
MA
Summers
M Sue
MS
O'Dorisio
Mary O
MO
Cox
Maria
M
Lara-Marquez
Edward J
EJ
Goetzl
D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D019073:HT29 Cells; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D018005:Receptors, Vasoactive Intestinal Peptide / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000502:physiology; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D010446:Peptide Fragments; D010455:Peptides; D018005:Receptors, Vasoactive Intestinal Peptide; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; C113198:vasoactive intestinal peptide (6-28); D014660:Vasoactive Intestinal Peptide; C047945:vasoactive intestinal peptide (10-28)