What is "thapsigargin"

n. (context biochemistry English) A sesquiterpene lactone that is an inhibitor of a certain class of enzymes

Thapsigargin is non-competitive inhibitor of the sarco/ endoplasmic reticulum Ca 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.

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