Pituitary Adenylate Cyclase-Activating Polypeptide and Sonic Hedgehog Interact to Control Cerebellar Granule Precursor Cell Proliferation

Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 12/2002; 22(21):9244-54.
Source: PubMed


Although positive and negative signals control neurogenesis in the embryo, factors regulating postnatal proliferation are less well characterized. In the vertebrate cerebellum, Sonic Hedgehog (Shh) is an efficacious mitogen for cerebellar granule neuron precursors (GNPs), and mutations activating the Shh pathway are linked to medulloblastoma, a tumor derived from GNPs. Although the mitogenic effects of Shh can be blocked by increasing cAMP or protein kinase A activity, the physiological factors antagonizing this stimulation are undefined. In the embryo, pituitary adenylate cyclase-activating polypeptide (PACAP) receptor 1 (PAC1) signaling regulates neural precursor proliferation. We now show that in the developing cerebellum, PAC1 mRNA colocalizes with gene transcripts for Shh receptor Patched 1 and target gene Gli1 in the external germinal layer. We consequently investigated the interactions of PACAP and Shh in proliferation of purified GNPs in culture. Shh exhibited mitogenic activity in both rat and mouse cultures, stimulating DNA synthesis approximately 10-fold after 48 hr of exposure. PACAP markedly inhibited Shh-induced thymidine incorporation by 50 and 85% in rat and mouse GNPs, respectively, but did not significantly affect the stimulation induced by other mitogens. This selective effect was reproduced by the specific PAC1 agonist maxadilan, as well as by the adenylate cyclase activator forskolin, suggesting that PAC1 provides a potent inhibitory signal for Shh-induced proliferation in developing cerebellum. In contrast, in the absence of Shh, PACAP and maxadilan modestly stimulated DNA synthesis, an effect reproduced by activating protein kinase C. These observations suggest that G-protein-coupled receptors, such as PAC1, serve as sensors of environmental cues, coordinating diverse neurogenetic signals.

Download full-text


Available from: Vincent Lelièvre, Oct 10, 2015
6 Reads
  • Source
    • "lung cancer ( Pullamsetti et al . , 2013 ) and colon cancer ( McEwan et al . , 2007 ) . Similar to the case for polymorphisms in ADCY and cancer risk , single nucleotide variations in PDE8A and PDE11A have been associated with adrenocortical carcinoma ( Oliver et al . , 2005 ) as well as cancer of the testes ( Klein et al . , 2001 ) and prostate ( Nicot et al . , 2002 ) ."
    [Show abstract] [Hide abstract]
    ABSTRACT: A relationship between cyclic adenosine 3', 5'-monophosphate (cAMP) levels and brain tumor biology has been evident for nearly as long as cAMP and its synthetase, adenylate cyclase (ADCY) have been known. The importance of the pathway in brain tumorigenesis has been demonstrated in vitro and in multiple animal models. Recently, we provided human validation for a cooperating oncogenic role for cAMP in brain tumorigenesis when we found that SNPs in ADCY8 were correlated with glioma (brain tumor) risk in individuals with Neurofibromatosis type 1 (NF1). Together, these studies provide a strong rationale for targeting cAMP in brain tumor therapy. However, the cAMP pathway is well-known to be sexually dimorphic, and SNPs in ADCY8 affected glioma risk in a sex-specific fashion, elevating the risk for females while protecting males. The cAMP pathway can be targeted at multiple levels in the regulation of its synthesis and degradation. Sex differences in response to drugs that target cAMP regulators indicate that successful targeting of the cAMP pathway for brain tumor patients is likely to require matching specific mechanisms of drug action with patient sex.
    Frontiers in Pharmacology 08/2015; 6:153. DOI:10.3389/fphar.2015.00153 · 3.80 Impact Factor
  • Source
    • "The effect of cPA appears to be similar to that of PACAP and NOV, both known suppressors of the Shh-dependent cell proliferation in cerebellar GCPs (Le Dreau et al., 2009; Nicot et al., 2002). We also detected the presence of autotaxin mRNA, a synthetic enzyme of cPA, in GCPs (data not shown). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The proliferation and differentiation of cerebellar granule cell precursors (GCPs) are highly regulated spatiotemporally during development. We focused on cyclic phosphatidic acid (cPA) as a lipid mediator with a cyclic phosphate group as a regulatory factor of GCPs. While its structure is similar to that of lysophosphatidic acid (LPA), its function is very unique. cPA is known to be present in the cerebellum at high levels, but its function has not been fully elucidated. In this study, we examined the role of cPA on the proliferation and differentiation of GCPs. A cell cycle analysis of GCPs revealed that cPA reduced the number of phospho-histone H3 (Phh3)-positive cells and bromodeoxy uridine (BrdU)-incorporated cells and increased an index of the cell cycle exit. We next analyzed the effect of cPA on GCP differentiation using Tuj1 as a neuronal marker. The results show that cPA increased the number of Tuj1-positive cells. Further analysis of the proliferation of GCPs showed that cPA suppressed Sonic hedgehog (Shh)-dependent proliferation, but did not suppress insulin-like growth factor-1 (IGF-1)-dependent proliferation. P2Y5 (LPA6), an LPA receptor, is highly expressed in GCPs. The knockdown of P2Y5 suppressed the inhibitory effect of cPA on the proliferation of GCPs, suggesting that P2Y5 is a candidate receptor for cPA. Thus, cPA suppresses the Shh-dependent proliferation of GCPs and promotes the differentiation of GCPs through P2Y5. These results demonstrate that cPA plays a critical role in the development of GCPs. Copyright © 2015. Published by Elsevier B.V.
    Brain research 04/2015; 17. DOI:10.1016/j.brainres.2015.04.013 · 2.84 Impact Factor
  • Source
    • "PACAP influences several signaling pathways and neurotrophins also involved in the tooth development. In most experiments, PACAP behaves as an antagonist for bone morphogenetic protein-4 and SHH (Otto et al. 2000; Nicot et al. 2002; Lelievre et al. 2006; Hirose et al. 2011; Niewiadomski et al. 2013), two of the main most widely studied signaling pathways of the tooth development (Dassule et al. 2000; Jernvall and Thesleff 2000; Thesleff 2006; Bei 2009). Activation of PKA, regulated by PACAP receptors, can inhibit the transcriptional function of Gli1, consequently PACAP-induced signaling cascade is considered as a SHH signaling suppressor in neuronal elements (Hirose et al. 2011; Niewiadomski et al. 2013). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic neuropeptide with widespread distribution. It plays pivotal role in neuronal development. PACAP-immunoreactive fibers have been found in the tooth pulp, and recently, it has been shown that PACAP may also play a role in the regeneration of the periodontium after luxation injuries. However, there is no data about the effect of endogenous PACAP on tooth development. Ectodermal organogenesis including tooth development is regulated by different members of bone morphogenetic protein (BMP), fibroblast growth factor (FGF), hedgehog (HH), and Wnt families. There is also a growing evidence to support the hypothesis that PACAP interacts with sonic hedgehog (SHH) receptor (PTCH1) and its downstream target (Gli1) suggesting its role in tooth development. Therefore, our aim was to study molar tooth development in mice lacking endogenous PACAP. In this study morphometric, immunohistochemical and structural comparison of molar teeth in pre-eruptive developmental stage was performed on histological sections of 7-day-old wild-type and PACAP-deficient mice. Further structural analysis was carried out with Raman microscope. The morphometric comparison of the 7-day-old samples revealed that the dentin was significantly thinner in the molars of PACAP-deficient mice compared to wild-type animals. Raman spectra of the enamel in wild-type mice demonstrated higher diversity in secondary structure of enamel proteins. In the dentin of PACAP-deficient mice higher intracrystalline disordering in the hydroxyapatite molecular structure was found. We also obtained altered SHH, PTCH1 and Gli1 expression level in secretory ameloblasts of PACAP-deficient mice compared to wild-type littermates suggesting that PACAP might play an important role in molar tooth development and matrix mineralization involving influence on SHH signaling cascade.
    Journal of Molecular Neuroscience 08/2014; 54(3). DOI:10.1007/s12031-014-0392-6 · 2.34 Impact Factor
Show more