Thapsigargin

Thapsigargin is non-competitive inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA).[1] Structurally, thapsigargin is classified as a sesquiterpene lactone, and is extracted from a plant, Thapsia garganica.[2] It is a tumor promoter in mammalian cells.[3]

Thapsigargin
Names
IUPAC name
(3S,3aR,4S,6S,6aR,7S,8S,9bS)-6-(Acetyloxy)-4-(butyryloxy)-3,3a-dihydroxy-3,6,9-trimethyl-8-{[(2Z)-2-methylbut-2-enoyl]oxy}-2-oxo-2,3,3a,4,5,6,6a,7,8,9b-decahydroazuleno[4,5-b]furan-7-yl octanoate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.116.539
UNII
Properties
C34H50O12
Molar mass 650.762 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Thapsigargin raises cytosolic (intracellular) calcium concentration by blocking the ability of the cell to pump calcium into the sarcoplasmic and endoplasmic reticula. Store-depletion can secondarily activate plasma membrane calcium channels, allowing an influx of calcium into the cytosol. Depletion of ER calcium stores leads to ER stress and activation of the unfolded protein response.[4] Non-resolved ER stress can cumulatively lead to cell death.[5][6]

Thapsigargin treatment and the resulting ER calcium depletion inhibits autophagy independent of the UPR response.[7][8]

Thapsigargin is useful in experimentation examining the impacts of increasing cytosolic calcium concentrations and ER calcium depletion.

Biosynthesis

The complete biosynthesis of thapsigargin has yet to be elucidated. A proposed biosynthesis starts with the farnesyl pyrophosphate. The first step is controlled by the enzyme germacrene B synthase. In the second step, the C(8) position is easily activated for an allylic oxidation due to the position of the double bond. The next step is the addition of the acyloxy moiety by a P450 acetyltransferase; which is a well known reaction for the synthesis of the diterpene, taxol. In the third step, the lactone ring is formed by a cytochrome P450 enzyme using NADP+. With the butyloxy group on the C(8), the formation will only generate the 6,12-lactone ring. The fourth step is an epoxidation that initiates the last step of the base guaianolide formation. In the fifth step, a P450 enzyme closes the 5 + 7 guaianolide structure. The ring closing is important, because it will proceed via 1,10 - epoxidation in order to retain the 4,5 - double bond needed in thapsigargin. It is not known whether the secondary modifications to the guaianolide occur before, or after the formation of thapsigargin, but will need to be considered when elucidating the true biosynthesis. It should also be noted, that several of these enzymes are P450s, therefore oxygen and NADPH are likely crucial to this biosynthesis as well as other cofactors such as Mg2+ and Mn2+ may be needed.[9]

Research

Since inhibition of SERCA is a mechanism of action that has been used to target solid tumors, thapsigargin has attracted research interest. A prodrug of thapsigargin, mipsagargin, is currently undergoing clinical trials for the treatment of glioblastoma.[10][11][12][13]

The biological activity has also attracted research into the laboratory synthesis of thapsigargin. To date, three distinct syntheses have been reported: one by Steven V. Ley,[14] one by Phil Baran.,[15] and one by P. Andrew Evans.[16]

Preclinical studies demonstrated that other effects of thapsigargin include suppression of nicotinic acetylcholine receptors activity in neurons of the guinea-pig ileum submucous plexus[17] and rat superior cervical ganglion.[18]

gollark: Or something something nontrivial zeroes of the Riemann zeta function.
gollark: Chemistry/physics/maths/CS etc. are even more broadly defined and complex though, bad examples.
gollark: Yes, knowledge has improved in an absolute sense but apparently vaccine trials are still only successful 1/3 of the time generally.
gollark: You can get it *later*, probably.
gollark: The annoying thing is that, regardless of whether the mRNA ones *are* actually bad at all, with wide enough deployment someone will get a heart attack or something after getting it due to sheer random chance and people will start complaining.

See also

References
  1. Rogers TB, Inesi G, Wade R, Lederer WJ (1995). "Use of thapsigargin to study Ca2+ homeostasis in cardiac cells". Biosci. Rep. 15 (5): 341–9. doi:10.1007/BF01788366. PMID 8825036.
  2. Rasmussen U, Brøogger Christensen S, Sandberg F (1978). "Thapsigargine and thapsigargicine, two new histamine liberators from Thapsia garganica L.". Acta Pharm. Suec. 15 (2): 133–140. PMID 79299.CS1 maint: multiple names: authors list (link)
  3. Hakii, H.; Fujiki, H.; Suganuma, M.; Nakayasu, M.; Tahira, T.; Sugimura, T.; Scheuer, P. J.; Christensen, S. B. (1986). "Thapsigargin, a histamine secretagogue, is a non-12-O-tetradecanolphorbol-13-acetate (TPA) type tumor promoter in two-stage mouse skin carcinogenesis". Journal of Cancer Research and Clinical Oncology. 111 (3): 177–181. doi:10.1007/BF00389230. PMID 2426275.
  4. Malhotra, Jyoti D.; Kaufman, Randal J. (December 2007). "The endoplasmic reticulum and the unfolded protein response". Seminars in Cell & Developmental Biology. 18 (6): 716–731. doi:10.1016/j.semcdb.2007.09.003. PMC 2706143. PMID 18023214.
  5. Hetz, Claudio; Papa, Feroz R. (January 2018). "The Unfolded Protein Response and Cell Fate Control". Molecular Cell. 69 (2): 169–181. doi:10.1016/j.molcel.2017.06.017. PMID 29107536.
  6. Sano, Renata; Reed, John C. (2013-12-01). "ER stress-induced cell death mechanisms". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1833 (12): 3460–3470. doi:10.1016/j.bbamcr.2013.06.028. ISSN 0167-4889. PMC 3834229. PMID 23850759.
  7. Engedal, Nikolai; Torgersen, Maria L; Guldvik, Ingrid J; Barfeld, Stefan J; Bakula, Daniela; Sætre, Frank; Hagen, Linda K; Patterson, John B; Proikas-Cezanne, Tassula (2013-10-25). "Modulation of intracellular calcium homeostasis blocks autophagosome formation". Autophagy. 9 (10): 1475–1490. doi:10.4161/auto.25900. ISSN 1554-8627. PMID 23970164.
  8. Ganley, Ian G.; Wong, Pui-Mun; Gammoh, Noor; Jiang, Xuejun (2011). "Distinct Autophagosomal-Lysosomal Fusion Mechanism Revealed by Thapsigargin-Induced Autophagy Arrest" (PDF). Molecular Cell. 42 (6): 731–743. doi:10.1016/j.molcel.2011.04.024. PMID 21700220.
  9. Drew, D.P.; Krichau, N.; Reichwald, K.; Simonsen, H.T. (2009). "Guaianolides in apiaceae: perspectives on pharmacology and biosynthesis". Phytochem Rev. 8 (3): 581–599. doi:10.1007/s11101-009-9130-z.
  10. Denmeade, S. R.; Mhaka, A. M.; Rosen, D. M.; Brennen, W. N.; Dalrymple, S; Dach, I; Olesen, C; Gurel, B; Demarzo, A. M.; Wilding, G; Carducci, M. A.; Dionne, C. A.; Møller, J. V.; Nissen, P; Christensen, S. B.; Isaacs, J. T. (2012). "Engineering a Prostate-Specific Membrane Antigen–Activated Tumor Endothelial Cell Prodrug for Cancer Therapy". Science Translational Medicine. 4 (140): 140ra86. doi:10.1126/scitranslmed.3003886. PMC 3715055. PMID 22745436.
  11. Andersen, Trine; López, Carmen; Manczak, Tom; Martinez, Karen; Simonsen, Henrik (2015). "Thapsigargin—From Thapsia L. To Mipsagargin". Molecules. 20 (4): 6113–27. doi:10.3390/molecules20046113. PMC 6272310. PMID 25856061.
  12. "Mipsagargin". NCI Drug Dictionary. National Cancer Institute. 2011-02-02.
  13. "Clinical Trials: Mipsagargin". National Cancer Institute.
  14. Ball, Matthew; Andrews, Stephen P.; Wierschem, Frank; Cleator, Ed; Smith, Martin D.; Ley, Steven V. (2007). "Total Synthesis of Thapsigargin, a Potent SERCA Pump Inhibitor". Organic Letters. 9 (4): 663–6. doi:10.1021/ol062947x. PMID 17256950.
  15. Chu, Hang; Smith, Joel M.; Felding, Jakob; Baran, Phil S. (2017). "Scalable Synthesis of (−)-Thapsigargin". ACS Central Science. 3 (1): 47–51. doi:10.1021/acscentsci.6b00313. PMC 5269647. PMID 28149952.
  16. Chen, Dezhi; Evans, P Andrew. (2017). "A Concise, Efficient and Scalable Total Synthesis of Thapsigargin and Nortrilobolide from (R)-(-)-Carvone". J. Am. Chem. Soc. 139 (17): 6046–6049. doi:10.1021/jacs.7b01734. PMID 28422492.
  17. Glushakov, A. V.; Glushakova, H. Y.; Skok, V. I. (1999-01-15). "Modulation of nicotinic acetylcholine receptor activity in submucous neurons by intracellular messengers". Journal of the Autonomic Nervous System. 75 (1): 16–22. doi:10.1016/S0165-1838(98)00165-9. ISSN 0165-1838. PMID 9935265 – via https://doi.org/10.1016/S0165-1838(98)00165-9.
  18. Voitenko, S. V.; Bobryshev, A. Yu; Skok, V. I. (2000-01-01). "Intracellular regulation of neuronal nicotinic cholinorceptors". Neuroscience and Behavioral Physiology. 30 (1): 19–25. doi:10.1007/BF02461388. ISSN 0097-0549. PMID 10768368.

Further reading
  • Duncan G, Wormstone IM, Liu CS, Marcantonio JM, Davies PD (September 1997). "Thapsigargin-coated intraocular lenses inhibit human lens cell growth". Nat. Med. 3 (9): 1026–8. doi:10.1038/nm0997-1026. PMID 9288732.
  • Ibaraki N (September 1997). "A brighter future for cataract surgery". Nat. Med. 3 (9): 958–60. doi:10.1038/nm0997-958. PMID 9288718.
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