Abstract
Store-operated calcium entry (SOCE) is the main Ca(2+) influx pathway involved in controlling proliferation of the human hepatoma cell lines Huh-7 and HepG2. However, the molecular nature of the calcium channels involved in this process remains unknown. Huh-7 and HepG2 cells express transient receptor potential canonical 1 (TRPC1) and TRPC6, as well as STIM1 and Orai1, and these 4 channels are the most likely candidates to account for the SOCE in these cells. We generated stable TRPC6-overexpressing or TRPC6-knockdown Huh-7 clones, in which we investigated correlations between the presence of the protein, the rate of cell proliferation, and SOCE amplitude. TRPC6-overexpressing Huh-7 cells proliferated 80% faster than did untransfected cells and their SOCE amplitude was 160% higher. By contrast, proliferation rate was 50% lower and SOCE amplitude 85% lower in TRPC6-knockdown clones than in untransfected cells. OAG (olyl acetyl glycerol)-induced calcium entry was similar in all cells, and small interfering RNA (siRNA) against TRPC1 had no effect on SOCE amplitude, highlighting the relationship among SOCE, TRPC6 and cell proliferation in Huh-7 cells. SOCE amplitude was reduced by STIM1 and Orai1 knockdowns, suggesting possible cooperation between these proteins and TRPC6 in these cells. Endothelial growth factor and hepatocyte growth factor increased TRPC6 expression and SOCE amplitude in Huh-7 cells, and cyclin D1 expression was decreased by STIM1, Orai1, and TRPC6 knockdowns. TRPC6 was very weakly expressed in isolated hepatocytes from healthy patients and expressed more strongly in tumoral samples from the liver of a cancer patient, strongly supporting a role for these calcium channels in liver oncogenesis.
Highlights
To cite this version: Charbel El Boustany, Gabriel Bidaux, Antoine Enfissi, Philippe Delcourt, Natalia Prevarskaya, et al
Little is known about the role of these channels in hepatocytes, and 1 previous study has reported the involvement of transient receptor potential canonical 1 (TRPC1) in Store-operated calcium entry (SOCE) activation.[8]. Both transient receptor potential canonical 6 (TRPC6) and TRPC1 have been associated with cell proliferation and SOCE,[9] and we recently showed that SOCE is essential for human hepatoma cell line proliferation.[10]
TRPC6 is often described as a channel involved in noncapacitative calcium entry (NCCE),[21,22] but there is evidence to suggest it is involved in SOCE in some tissues.[9,11]
Summary
To cite this version: Charbel El Boustany, Gabriel Bidaux, Antoine Enfissi, Philippe Delcourt, Natalia Prevarskaya, et al. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Huh-7 and HepG2 cells express transient receptor potential canonical 1 (TRPC1) and TRPC6, as well as STIM1 and Orai[1], and these 4 channels are the most likely candidates to account for the SOCE in these cells. The processes involved in the transformation of normal cells into tumorigenic cells and tumor progression are complex and only partially understood.[1,2] Many proteins in cancer cells are produced in Abbreviations used: SOCE, store-operated calcium entry; STIM1, stromal interacting molecule 1; NCCE, noncapacitative calcium entry; TRPC6, transient receptor potential canonical 6; OAG, 1-oleoy1-2-acetyl-glycerol
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