Thapsigargin

Thapsigargin is non-competitive inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA). Structurally, thapsigargin is classified as a sesquiterpene lactone, and is extracted from a plant, Thapsia garganica. It is a tumor promoter in mammalian cells. Thapsigargin is non-competitive inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA). Structurally, thapsigargin is classified as a sesquiterpene lactone, and is extracted from a plant, Thapsia garganica. It is a tumor promoter in mammalian cells. 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. Thapsigargin specifically inhibits the fusion of autophagosomes with lysosomes; the last step in the autophagic process. The inhibition of the autophagic process in turn induces stress on the endoplasmic reticulum which ultimately leads to cellular death.