PAC1-expressing structures of neural retina alter their PAC1 isoform splicing during postnatal development

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin/glucagon/vasoactive intestinal peptide family, exerts various effects on neuronal development as mediated by the differential expression of PAC1 receptor (PAC1-R) isoforms. The expression changes of PAC1-R isoforms (Hip, Hop1) reported in correlation with retinal development suggest an isoform switch during the second postnatal week. Our aim is to determine the exact period of the isoform shift and to describe the PAC1-R-immunoreactive structures appearing from postnatal day 5 (P5) to P10 in the rat retina. The ratio of Hip and Hop1 receptors was assessed and changes in their expression were followed by Taqman and SybrGreen-based quantitative polymerase chain reaction. For the detection of PAC1-R-expressing retinal structures, anti-PAC1-R, anti-calbindin, anti-protein kinase C, anti-glutamine synthetase, anti-HPC1 and anti-Brn3a antibodies were utilized. At the transcript level, a marked decrease to an undetectable level was measured in Hip mRNA expression from P6 to P9. Hop1 expression appeared to be unchanged from P6 to P9, followed by a significant elevation at P10. A Hip/Hop1 isoform shift occurred between P6 and P7. Immunostaining showed strong PAC1-R labeling from P5 to P10 in ganglion, amacrine, horizontal and rod bipolar neurons and in glial Muller cell processes. The Hop1 isoform was predominantly expressed in various types of retinal cell beginning at P7, because of a dramatic reduction in Hip mRNA level. As the Hop1 receptor is coupled to different signaling cascades, this isoform shift might alter the physiological role of PACAP during this particular period.

Review on PACAP-Induced Transcriptomic and Proteomic Changes in Neuronal Development and Repair

“…PACAP has been described in the proliferation and differentiation of various neuronal cell lines, such as cortical neuroblasts [ 47 ], cerebellar granule cells [ 48 , 49 ], retinoblasts [ 50 , 51 ], sympathetic neuroblasts [ 52 ] and olfactory neuroblasts [ 53 ], detailed transcriptomic studies are available on adrenal cells. Data from chromaffin cells (PC12 pheochromocytoma cells) have been reviewed by Samal et al [ 32 ], providing a thorough meta-analysis of PACAP-regulated genes.…”

Pituitary Adenylate Cyclase-Activating Peptide (PACAP), a Novel Secretagogue, Regulates Secreted Morphogens in Newborn Rat Retina

“…18,28 However, in the present study, we aimed to point out that the versatility cannot be understood only through diversity of PACAP1-38 receptors. Instead, interaction with other regulators should be considered in which the PACAP1-38 can act directly and indirectly on the retinal microenvironment and evolve a complex array of function.…”

Pituitary Adenylate Cyclase-Activating Polypeptide: 30 Years in Research Spotlight and 600 Million Years in Service

“…They show differential regulation in development indicating functional significance. [12,13]. The isoforms affect ligand-binding selectivities and may control the signaling bias.…”

“…The complexity of PACAP receptors is further increased by PAC1 receptor (PAC1-R) isoforms through alternative splicing at the transcript level. In vertebrates, 20 PAC1-R isoforms have been identified [11], primarily in cell lines in vitro, but a number of them have also been verified in vivo with development-related expression patterns [12,13]. The isoforms were shown to affect ligand-binding selectivities and signaling mechanisms, but, in contrast to the large number of isoforms, only a few signal pathways are utilized.…”