Inhibition of expression of the type I G protein-coupled receptor for vasoactive intestinal peptide (VPAC1) by hammerhead ribozymes.
Vasoactive intestinal peptide (VIP) is a neuromediator expressed widely in the nervous, gastrointestinal, respiratory, and immune systems. Two G protein-coupled receptors (GPCRs), designated VPAC1 and VPAC2, bind VIP with high affinity and transduce increases in [cyclic AMP](i) and [Ca(2+)](i). As there are no potent VPAC1- or VPAC2-selective antagonists, a hammerhead ribozyme (Rz) strategy capable of in vivo application was adopted to inactivate individual domains of VPAC1. Three Rzs were designed to cleave mRNA encoding the amino terminus, the third intracellular loop, and the cytoplasmic tail of human VPAC1 and were introduced by transfection into HEK-293 cells expressing recombinant human VPAC1. Each Rz specifically degraded VPAC1 mRNA and down-regulated VPAC1 protein and VIP-binding activity, as assessed by ribonuclease protection assays, Western blots, and binding of (125)I-VIP. Rz-mediated down-regulation of VPAC1 was associated with up to 75% suppression of VIP signaling of increases in [cyclic AMP](i) and [IP3](i), and of cyclic AMP response element-luciferase reports. The Rz specific for the amino terminus inhibited VPAC1 expression and signaling to the greatest extent. VIP-evoked cellular responses thus appear to be proportional to the level of VPAC1 expression. Specific Rzs may be powerful tools for manipulating tissue-specific contributions of GPCRs in vitro and in vivo.
Jabrane-Ferrat
N
N
Departments of Medicine and Microbiology-Immunology and Department of Medicine, Veterans Affairs Medical Center, University of California, San Francisco, California 94143-0711, USA.
Pollock
A S
AS
Goetzl
E J
EJ
D000595:Amino Acid Sequence; D019204:GTP-Binding Proteins; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D018005:Receptors, Vasoactive Intestinal Peptide / Q000096:biosynthesis* / Q000235:genetics; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I
D007295:Inositol Phosphates; D016337:RNA, Catalytic; D012333:RNA, Messenger; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D019204:GTP-Binding Proteins