Regulation by protein kinase-C of putative P-type Ca channels expressed in Xenopus oocytes from cerebellar mRNA

AbstractXenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and ω-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels. The precise nature of the transplanted Ca channels was assessed by hybrid-arrest experiments using a specific oligonucleotide antisense-derivated from the recently cloned α1-subunit of P channels (BI-1 clone). In addition, we demonstrate that exogenous Ca channel activity was enhanced by two different PKC activators (a phorbol ester and a structural analog to diacylglycerol). The general electrophysiological and pharmacological properties of the stimulated Ca channels remain unchanged. This potentiation induced by PKC activators is antagonized by a PKC inhibitor (staurosporine) and by a monoclonal antibody directed against PKC. It is concluded that P-type Ca channels are potentially regulated by PKC phosphorylation and the functional relevance of this intracellular pathway is discussed

Implication du canal BK dans l'effet des oestrogènes et du tamoxifène sur la prolifération des cellules cancéreuses mammaires humaines

Le cancer du sein est la néoplasie la plus fréquente chez la femme et représente un problème majeur de santé publique. La cancérogenèse mammaire implique clairement les œstrogènes dont l action repose sur l activation de deux voies de signalisation : une voie génomique régulant l expression de gènes cibles et une voie alternative mise en place rapidement et indépendamment d une activité transcriptionnelle. Au vu de l œstrogèno-dépendance du cancer du sein, les principaux traitements visent à antagoniser l action de ces hormones grâce à des composés anti-œstrogèniques tel que le tamoxifène. Par ailleurs, il a été montré que la prolifération et l apoptose des cellules cancéreuses mammaires sont régulées par des canaux potassiques. Le but de ma thèse a été d étudier la régulation des canaux potassiques par les œstrogènes et les anti-œstrogènes et de déterminer si cette régulation pouvait être impliquée dans les effets de ces facteurs sur la croissance des cellules cancéreuses mammaires humaines. Nos résultats montrent que de faibles doses de 17 ß œstradiol et de tamoxifène activent le canal potassique de grande conductance (BK) dans les cellules cancéreuses mammaires humaines de la lignée MCF-7 et que cet effet est impliqué dans l augmentation de leur prolifération. De plus, nous avons montré que les sous unités ß1 et ß4 des canaux BK semblent être impliquées dans leur modulation par ces facteurs. Par ailleurs, nous avons mis en évidence que de fortes doses de tamoxifène diminuent la croissance de ces cellules et modulent de manière bimodale un canal potassique voltage- et calcium-dépendant. Nous proposons que l activation du canal BK par le 17 ß œstradiol permettrait d accentuer l hyperpolarisation membranaire liée à la progression des cellules cancéreuses mammaires dans le cycle cellulaire. En conclusion, nos résultats nous permettent de proposer que les effets des œstrogènes et du tamoxifène sur le canal BK devraient être pris en compte dans la mise au point de traitements plus efficaces du cancer du sein.AMIENS-BU Santé (800212102) / SudocSudocFranceF

Inositol 1,4,5-trisphosphate-induced Ca2+ signalling is involved in estradiol-induced breast cancer epithelial cell growth

BACKGROUND: Ca2+ is a ubiquitous messenger that has been shown to be responsible for controlling numerous cellular processes including cell growth and cell death. Whereas the involvement of IP3-induced Ca2+ signalling (IICS) in the physiological activity of numerous cell types is well documented, the role of IICS in cancer cells is still largely unknown. Our purpose was to characterize the role of IICS in the control of growth of the estrogen-dependent human breast cancer epithelial cell line MCF-7 and its potential regulation by 17beta-estradiol (E2). RESULTS: Our results show that the IP3 receptor (IP3R) inhibitors caffeine, 2-APB and xestospongin C (XeC) inhibited the growth of MCF-7 stimulated by 5% foetal calf serum or 10 nM E2. Furthermore, Ca2+ imaging experiments showed that serum and E2 were able to trigger, in a Ca2+-free medium, an elevation of internal Ca2+ in a 2-APB and XeC-sensitive manner. Moreover, the phospholipase C (PLC) inhibitor U-73122 was able to prevent intracellular Ca2+ elevation in response to serum, whereas the inactive analogue U-73343 was ineffective. Western-blotting experiments revealed that the 3 types of IP3Rs are expressed in MCF-7 cells and that a 48 hours treatment with 10 nM E2 elevated IP3R3 protein expression level in an ICI-182,780 (a specific estrogen receptor antagonist)-dependent manner. Furthermore, IP3R3 silencing by the use of specific small interfering RNA was responsible for a drastic modification of the temporal feature of IICS, independently of a modification of the sensitivity of the Ca2+ release process and acted to counteract the proliferative effect of 10 nM E2. CONCLUSIONS: Altogether, our results are in favour of a role of IICS in MCF-7 cell growth, and we hypothesize that the regulation of IP3R3 expression by E2 is involved in this effect.status: publishe

The 22nd Ion Channel Meeting, September 2011, France

International audienc

The 22nd ion channel meeting, september 2011, france.

International audienceThe 22(nd) Ion Channel Meeting was organized by the French Ion Channel Society (Association Canaux Ioniques) from the 25(th) to the 28(th) of September 2011 on the French Riviera (Giens). This year again, more than one hundred researchers from France, Europe and extra-European countries gathered to present and discuss their recent advances and future challenges in the ion channels and transporters field. The scientific committee organized a plenary lecture and five thematic symposia by inviting international researchers to present their recent outstanding work on themes as diverse as muscular channelopathies, regulation of channels by extracellular matrix, receptor-channels interactions, localization and distribution of ion channels, their involvement in the cell life and death, and finally how they participate in the evolution and adaptability of cellular excitability. These presentations are summarized in this meeting report. Two sessions of oral communications selected from submitted abstracts and two poster sessions were also organized to present the ongoing work of young researchers worldwide