Basiliolides, a class of tetracyclic C19 dilactones from Thapsia garganica, release Ca(2+) from the endoplasmic reticulum and regulate the activity of the transcription factors nuclear factor of activated T cells, nuclear factor-kappaB, and activator protein 1 in T lymphocytes.
Calcium concentration within the endoplasmic reticulum (ER) plays an essential role in cell physiology. We have investigated the effects of basiliolides, a novel class of C19 dilactones isolated from Thapsia garganica, on Ca(2+) mobilization in T cells. Basiliolide A1 induced a rapid mobilization of intracellular Ca(2+) in the leukemia T-cell line Jurkat. First, a rapid calcium peak was observed and inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. This initial calcium mobilization was followed by a sustained elevation, mediated by the entry of extracellular calcium through store-operated calcium release-activated Ca(2+) (CRAC) channels and sensitive to inhibition by EGTA, and by the CRAC channel inhibitor N-{4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl}-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP-2). Basiliolide A1 mobilized Ca(2+) from ER stores, but in contrast to thapsigargin, it did not induce apoptosis. Basiliolide A1 induced nuclear factor of activated T cells 1 dephosphorylation and activation that was inhibited by BTP-2 and cyclosporine A. In addition, we found that basiliolide A1 alone did not mediate IkappaBalpha degradation or RelA phosphorylation (ser536), but it synergized with phorbol 12-myristate 13-acetate to induce a complete degradation of the nuclear factor-kappaB inhibitory protein and to activate the c-Jun NH(2)-terminal kinase. Moreover, basiliolide A1 regulated both interleukin-2 and tumor necrosis factor-alpha gene expression at the transcriptional level. In basiliolide B, oxidation of one of the two geminal methyls to a carboxymethyl group retained most of the activity of basiliolide A1. In contrast, basiliolide C, where the 15-carbon is oxidized to an acetoxymethine, was much less active. These findings qualify these compounds as new probes to investigate intracellular calcium homeostasis.
Navarrete
Carmen
C
Departamento de Biología Celular, Fisiología e Inmunología, Facultad de Medicina, Avda. de Menéndez Pidal s/n, Universidad de Córdoba, 14004 Córdoba, Spain.
Sancho
Rocío
R
Caballero
Francisco J
FJ
Pollastro
Federica
F
Fiebich
Bernd L
BL
Sterner
Olov
O
Appendino
Giovanni
G
Muñoz
Eduardo
E
D019661:Apiaceae / Q000737:chemistry*; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D007783:Lactones / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D007783:Lactones; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D018808:Transcription Factor AP-1; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium