SERCA-Inhibiting Activity of C-19 Terpenolides from Thapsia garganica and Their Possible Biogenesis

Abstract

An investigation of Thapsia garganica afforded a series of tetracyclic C-19 dilactones, whose production was dependent on the time and location of the collection. These unusual tetrahomosesquiterpenoids are presumably biosynthesized via a carbon dioxide-triggered electrophilic polyolefin cyclization. Despite the structural differences with thapsigargin, these compounds showed SERCA-inhibiting properties.

Basiliolides, a Class of Tetracyclic C19 Dilactones fromThapsia garganica, Release Ca2+from the Endoplasmic Reticulum and Regulate the Activity of the Transcription Factors Nuclear Factor of Activated T Cells, Nuclear Factor-κB, and Activator Protein 1 in T Lymphocytes

“…The very tight binding of thapsigargin to all currently known SERCAs causes an irreversible inhibition that persists after removal of the excess inhibitor (Waldron et al, 1994), an observation that can explain, or contribute to, the potent apoptotic activity of this compound. Conversely, basiliolide A1 was unable to induce apoptosis in Jurkat cells, despite its alleged SERCA inhibitory activity (Appendino et al, 2005). It is therefore tempting to suggest that basiliolide A1 acts as a reversible SERCA inhibitor, not unlike 2,5-di-(tert-butyl)-1,4-benzohydroquinone, a SERCA blocker that protects HeLa cells from ceramide-induced apoptosis (Pinton et al, 2001).…”

“…The anti-phospho-ERK1 ϩ 2 (sc-7383) was from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA), and the mAbs anti-phospho-JNK (9255S) and anti-phospho-p65 (3031S) were from New England Biolabs (Hitchin, UK). Thapsigargin and the tetracyclic C19 dilactones basiliolide A1, B, and C were isolated from Thapsia garganica as described previously (Appendino et al, 2005). BTP-2 was from Calbiochem (San Diego, CA).…”

“…Separated proteins were transferred to nitrocellulose membranes (0.5 A at 100 V; 4°C) for 1 h. Blots were blocked in Tris-buffered saline solution containing 0.1% Tween 20 and 5% nonfat dry milk overnight at 4°C, and immunodetection of specific proteins was carried out with primary antibodies using an ECL system (GE Healthcare, Little Chalfont, Buckinghamshire, UK). (Appendino et al, 2005). To study the effects of these novel compounds in mammalian cells, the [Ca 2ϩ ] i in Indo1-loaded Jurkat cells was analyzed.…”

“…We have recently shown that, apart from TG, T. garganica also contains compounds capable of mobilizing Ca 2ϩ from the ER. These were identified in a series of unique C19 dilactones named basiliolides (Appendino et al, 2005).…”

“…We have recently shown that, apart from TG, T. garganica also contains compounds capable of mobilizing Ca 2ϩ from the ER. These were identified in a series of unique C19 dilactones named basiliolides (Appendino et al, 2005).In biological systems, calcium ions (Ca 2ϩ ) function as ubiquitous messengers that play an essential role in signal transThis work was supported by Ministerio de Educación y Ciencia Grant SAF2004-00926 (to E.M.).Article, publication date, and citation information can be found at …”