Paraptosis was recently described as a form of cell death characterized by extensive cytoplasmic vacuolation involving swelling of mitochondria and endoplasmic reticulum.

Paraptosis is thought to have some relationship with autophagy because of the presence of cytoplasmic vacuolation.

It is closely related to both necrosis and apoptosis.

Here are some key points to remember regarding paraptosis.

1. CASPASE INDEPENDENT: This form of cell death was not inhibited by the caspase inhibitors but is inhibited by translation and transcription inhibitors, cycloheximide and actinomycin D, suggesting a requirement for new protein synthesis.
2. Paraptosis has been shown to be triggered by the tumor necrosis factor (TNF) receptor family TAJ/TROY and insulin-like factor I receptor. TAJ/TROY-induced paraptotic cell death was enhanced by overexpression of programmed cell death 5 (PDCD5).
3. Glucocorticoids were shown to induce retinal toxicity by mechanisms associated with paraptosis. Although this form of cell death has been shown to be evoked by a variety of reagents, the exact molecular mechanism is far from clear.
4. CYTOPLASMIC VACUOLATION, as seen in paraptosis, has been shown to occur in a wide range of cell lines either spontaneously or as induced by a variety of stimuli. The extent to which a cell becomes vacuolated depends on the cell type. The process of vacuolation seems to follow a definite pattern, with the vacuole number and size increasing gradually. Cells can recover from vacuolation up to a certain threshold, beyond which they succumb to death.
5. The most studied cytoplasmic vacuolation-induced cell death is autophagy.

REVIEW QUESTION

1. Which of the following statements is true regarding paraptosis?

A. It is unrelated to necrosis and apoptosis

B. It is a caspase dependent pathway

C. Paraptosis is known to be triggered by TGF-beta related pathways.

D. Cytoplasmic vacuolation is a key feature of paraptosis.