Multiple splice variants of the pituitary adenylate cyclase-activating polypeptide type 1 receptor detected by RT-PCR in single rat pituitary cells

Abstract

Alternative splicing of the rat type 1 pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PVR1) produces variants that couple either to both adenylyl cyclase (AC) and phospholipase C (PLC) (PVR1 short, PVR1 hop, PVR1 hiphop), or to AC alone (PVR1 hip). We have previously shown that populations of clonal T3-1 gonadotrophs express PVR1 hop and PVR1 short mRNAs, whereas clonal GH 4 C 1 somatotrophs do not. Here we have used the single cell RT-PCR technique to investigate whether normal rat gonadotrophs and somatotrophs express PVR1 mRNA, whether a single cell co-expresses multiple splice variant forms, and whether differential PVR1 mRNA expression correlates with differences in PACAP-stimulated Ca 2+ signalling. We found that individual rat gonadotrophs expressed mRNA either for PVR1 hop, for PVR1 short, or co-expressed the two forms. Although we found no differences between the splice variant(s) expressed and the characteristics of PACAP-stimulated Ca 2+ responses, the expression of PVR1 mRNA is consistent with the known PACAP stimulation of the PLC system in gonadotrophs. Individual rat somatotrophs also expressed PVR1 hop or PVR1 short (but not PVR1 hip) mRNAs although these forms were never co-expressed. The expression of PVR1 mRNA in somatotrophs can explain in part the activation by PACAP of the AC system in such cells. In conclusion, the single cell RT-PCR technique was used to demonstrate expression of multiple PVR1 splice variants in single identified pituitary cells. These findings open up important questions on the role of alternative splicing in cell biology.

Vasoactive intestinal peptide signaling axis in human leukemia

“…In addition to VIP and PHM, activated mast cells and rat basophilic leukemia cell lines secrete a truncated VIP10-28 that acts as a potent VPAC1 antagonist, with low VPAC2 binding [11] . Couple this complexity to at least one splice variant of VPAC1, two for VPAC2 and 11 for PAC1, and the ability for the VIP ligand released by neurons innervating an immune organ can have a multitude of functional consequences [72,73] . Unpublished data from our laboratory has identified up to four additional VPAC1 splice variants present in lymphoid and brain cells.…”

PACAP/PAC1 autocrine system promotes proliferation and astrogenesis in neural progenitor cells

“…Accordingly, PACAP is considered to influence the regulation of NPC proliferation and/or differentiation during embryonic development . The PAC1 gene encodes a G-protein-coupled receptor that has four splice variants, depending on the presence or absence of either one or two of the cassettes, ''hip'' and ''hop,'' in the third intercellular loop (Bresson-Bepoldin et al, 1998;Jaworski and Proctor, 2000;Zhou et al, 2000a,b). These splice variants are involved in multiple and response-specific second messenger cascades (Pisegna et al, 1996).…”

Homer1 Alternative Splicing Is Regulated by Gonadotropin-Releasing Hormone and Modulates Gonadotropin Gene Expression

“…The Pvr1 gene encodes four major splice variant forms of the pituitary adenylate cyclase-activating polypeptide receptor; these variants differ in the sequence of the third intracellular loop, which is critical for G protein binding. As these variants display differences of affinity for G proteins and in their downstream signaling, this results in heterogeneous ligand responses in individual rat gonadotropes (43). In pituitary gonadotropes, a novel splice variant, Pitx2b2, employs the same 5= donor site as Pitx2b at intron 2 but an alternative 3= acceptor site, resulting in a 39-bp in-frame deletion.…”