Annie-Claire Meunier

Differential Expression and Function of PACAP and VIP Receptors in Four Human Colonic Adenocarcinoma Cell Lines

Human colonic adenocarcinoma cell lines have conserved several features of the native tissue. Among these is the expression of cell surface receptors for hormones and neurotransmitters that may be involved in the regulation of proliferation and differentiation processes in these cancer cells. Here, we confirm that high-affinity binding sites for the Vasoactive Intestinal Polypeptide (VIP) and for the VIP analogue Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP), were expressed in 4 human colonic adenocarcinoma cell lines, HT29, SW403, DLD-1 and Caco-2, that spontaneously displayed variable phenotypic properties in culture. We demonstrated that after long-term treatments, VIP and PACAP significantly reduced cell proliferation in the 4 cell lines and modulated intracellular cAMP and cGMP levels. Furthermore, conspicuous differences were observed from one cell type to another concerning expression of the receptor subsets or the effects of the neuropeptides on cell growth and on cyclic nucleotides production.

Unconventional binding sites and receptors for VIP and related peptides PACAP and PHI/PHM: An update

The 28-amino-acid neuropeptide VIP and related peptides PACAP and PHI/PHM modulate virtually all of the vital functions in the body. These peptides are also commonly recognized as major regulators of cell growth and differentiation. Through their trophic and cytoprotective functions, they appear to play major roles in embryonic development, neurogenesis and the progression of a number of cancer types. These peptides bind to three well-characterized subtypes of G-protein coupled receptors: VPAC1 and VPAC2 share a common high affinity in the nanomolar range for VIP and PACAP; a third receptor type, PAC1, has been characterized for its high affinity for PACAP but its low affinity for VIP. Complex effects and pharmacological behaviors of these peptides suggest that multiple subtypes of binding sites may cooperate to mediate their function in target cells and tissues. In this complex response, some of these binding sites correspond to the definition of the conventional receptors cited above, while others display unexpected pharmacological and functional properties. Here we present potential clues that may lead investigators to further characterize the molecular nature and functions of these atypical binding species.

A chimerical phagocytosis model reveals the recruitment by Sertoli cells of autophagy for the degradation of ingested illegitimate substrates.

Phagocytosis and autophagy are typically dedicated to degradation of substrates of extrinsic and intrinsic origins respectively. Although overlaps between phagocytosis and autophagy were reported, the use of autophagy for ingested substrate degradation by nonprofessional phagocytes has not been described. Blood-separated tissues use their tissue-specific nonprofessional phagocytes for homeostatic phagocytosis. In the testis, Sertoli cells phagocytose spermatid residual bodies produced during germ cell differentiation. In the retina, pigmented epithelium phagocytoses shed photoreceptor tips produced during photoreceptor renewal. Spermatid residual bodies and shed photoreceptor tips are phosphatidylserine-exposing substrates. Activation of the tyrosine kinase receptor MERTK, which is implicated in phagocytosis of phosphatidylserine-exposing substrates, is a common feature of Sertoli and retinal pigmented epithelial cell phagocytosis. The major aim of our study was to investigate to what extent phagocytosis by Sertoli cells may be tissue specific. We analyzed in Sertoli cell cultures that were exposed to either spermatid residual bodies (legitimate substrates) or retina photoreceptor outer segments (illegitimate substrates) the course of the main phagocytosis stages. We show that whereas substrate binding and ingestion stages occur similarly for legitimate or illegitimate substrates, the degradation of illegitimate but not of legitimate substrates triggers autophagy as evidenced by the formation of double-membrane wrapping, MAP1LC3A-II/LC3-II clustering, SQSTM1/p62 degradation, and by marked changes in ATG5, ATG9 and BECN1/Beclin 1 protein expression profiles. The recruitment by nonprofessional phagocytes of autophagy for the degradation of ingested cell-derived substrates is a novel feature that may be of major importance for fundamentals of both apoptotic substrate clearance and tissue homeostasis.

The vasoactive intestinal peptide-receptor system is involved in human glioblastoma cell migration

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumor in adults. This cancer has an infiltrative nature and the median survival of patients is about one year. Vasoactive intestinal peptide (VIP) belongs to a structurally related family of polypeptides and is a major regulatory factor in the central and peripheral nervous systems. VIP regulates proliferation of astrocytes and of numerous cancer cell lines and modulates migration in prostatic and colonic cancer cell lines. Little is known about the involvement of VIP and its receptors (VIP-receptor system) in proliferation or migration of GBM cells. The effects of VIP, PACAP and of synthetic VIP antagonists were tested in two human GBM cell lines, M059K and M059J, established from two different parts of a single tumor. In these cells, the data revealed that the VIP-receptor system did not affect proliferation but controlled cell migration. Indeed, in M059K cells which express components of the VIP receptor system, the VIP receptor antagonists and a PACAP antibody enhanced migration. The VIP receptor antagonists increased generation of typical migration-associated processes: filopodia and lamellipodia, and activation of Rac1 and Cdc42 GTPases. Reciprocally, in M059J cells which poorly express the VIP-receptor system, treatments with the agonists VIP and PACAP resulted in decreased cell migration. Furthermore, the peptides appeared to act through a subclass of binding sites displaying an uncommon very high affinity for these ligands. Taken together, these observations suggest that components of the VIP-receptor system negatively regulate cell migration, thus showing potential anti-oncogenic properties.

Naringin inhibits the invasion and migration of human glioblastoma cell via downregulation of MMP-2 and MMP-9 expression and inactivation of p38 signaling pathway

Gliomas are the most common and malignant primary brain tumors. They are associated with a poor prognosis despite the availability of multiple therapeutic options. Naringin, a common dietary flavonoid abundantly present in fruits and vegetables, is believed to possess strong anti-proliferative and anti-cancer properties. However, there are no reports describing its effects on the invasion and migration of glioblastoma cell lines. Our results showed that the treatment of U251 glioma cell lines with different concentrations of naringin inhibited the invasion and migration of these cells. In addition, we revealed a decrease in the levels of matrix metalloproteinases (MMP-2) and (MMP-9) expression as well as proteinase activity in U251 glioma cells. In contrast, the expression of tissue inhibitor of metalloproteinases (TIMP-1) and (TIMP-2) was increased. Furthermore, naringin treatment decreased significantly the phosphorylated level of p38. Combined treatment with a p38 inhibitor (SB203580) resulted in the synergistic reduction of MMP-2 and MMP-9 expressions correlated with an increase of TIMP-1 and TIMP-2 expressions and the anti-invasive properties. However, p38 chemical activator (anisomycin) could block these effects produced by naringin, suggesting a direct downregulation of the p38 signaling pathway. These data suggest that naringin may have therapeutic potential for controlling invasiveness of malignant gliomas by inhibiting of p38 signal transduction pathways.

Neuropeptides of the VIP family inhibit glioblastoma cell invasion

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are neuropeptides acting through VPAC1, VPAC2 and PAC1 receptors (referred here as the VIP-receptor system). In the central nervous system, VIP and PACAP are involved in neurogenesis, cell differentiation and migration, suggesting that they could be implicated in the development of glioblastoma (GBM). The infiltrative nature of GBM remains a major problem for the therapy of these tumors. We previously demonstrated that the VIP-receptor system regulated cell migration of the human cell lines M059J and M059K, derived from a single human GBM. Here, we evaluated the involvement of the VIP-receptor system in GBM cell invasion. In Matrigel invasion assays, M059K cells that express more the VIP-receptor system than M059J cells were less invasive. Invasion assays performed in the presence of agonists, antagonists or anti-PACAP antibodies as well as experiments with transfected M059J cells overexpressing the VPAC1 receptor indicated that the more the VIP-receptor system was expressed and activated, the less the cells were able to invade. Western immunoblotting experiments revealed that the VIP-receptor system inactivated the signaling protein AKT. Invasion assays carried out in the presence of an AKT inhibitor demonstrated the involvement of this signaling kinase in the regulation of cell invasion by the VIP-receptor system in M059K cells. The inhibition by VIP of invasion and AKT was also observed in U87 cells. In conclusion, VIP and PACAP act as anti-invasive factors in different GBM cell lines, a function mediated by VPAC1 inhibition of AKT signaling in M059K cells.

Phagocytosis by Sertoli Cells: Analysis of Main Phagocytosis Steps by Confocal and Electron Microscopy

Sertoli cells were discovered in the seminiferous tubules by Enrico Sertoli in 1865 (Morgagni 7:31-33, 1865). Intense phagocytosis is, in the context of spermatogenesis cycle, morphologically the most noticeable function of Sertoli cells. In this chapter the major principles of phagocytosis machinery and its specificities in the seminiferous tubules will be briefly reviewed, guidelines of analysis of main phagocytosis steps by confocal and transmission electron microscopy will be described, and a simplified method to assess phagocytosis rate in routine experiments will be given.

Myelinosomes act as natural secretory organelles in Sertoli cells to prevent accumulation of aggregate-prone mutant Huntingtin and CFTR.

Inappropriate deposition of insoluble aggregates of proteins with abnormal structures is a hallmark of affected organs in protein aggregation disease. Very rare, affected organs avoid aggregation naturally. This concerns atrophic testis in Huntington disease (HD). We aimed to understand how HD testis avoids aggregation. Using HD model R6/1 mice, we demonstrate that affected testis contain rare organelles myelinosomes. Myelinosomes secreted from testis somatic TM4 Sertoli cells provide the release of aggregate-prone mutant, but not normal Huntingtin (Htt) exon1. Myelinosomes also support the release of other aggregate-prone mutant protein responsible for cystic fibrosis (CF), F508delCFTR. The traffic and discharge of myelinosomes is facilitated by multivesicular bodies (MVB)s. Inhibition of MVB excretion induced reversible retention of both misfolded proteins inside TM4 Sertoli cells. We propose that myelinosome-mediated elimination of mutant proteins is an unusual secretory process allowing Sertoli cells getting rid of misfolded proteins to avoid aggregation and to maintain cell proteostasis.