Related Experiment Video
Updated: Jul 7, 2026

Measurements of Physiological Stress Responses in C. Elegans
Published on: May 21, 2020
Differential requirement of unfolded protein response pathway for calreticulin expression in Caenorhabditis elegans
Dukgyu Lee1, Gunasekaran Singaravelu, Byung-Jae Park
1Department of Life Science, Gwangju Institute of Science and Technology, 1 Oryong-Dong, Buk-Gu, Gwangju, Korea.
Abstract:
Accumulation of unfolded proteins in the endoplasmic reticulum triggers the unfolded protein response (UPR) pathway, which increases the expression of chaperones to maintain the homeostasis. Calreticulin is a calcium-binding chaperone located in the lumen of endoplasmic reticulum (ER). Here we show that in response to a UPR inducing reagent, tunicamycin, the expression of calreticulin (crt-1) is specifically up-regulated in Caenorhabditis elegans. Tunicamycin (TM) induced expression of the crt-1 requires IRE-1 and XBP-1 but is ATF-6 and PEK-1 independent. Analysis of the crt-1 promoter reveals a putative XBP-1 binding site at the -284 to -278 bp region, which was shown to be necessary for TM-mediated induction. Genetic analysis of crt-1 mutants and mutants of UPR pathway genes show various degrees of developmental arrest upon TM treatment. Our results suggest that the TM-induced UPR pathway culminates in the up-regulation of crt-1, which protects the worm from deleterious accumulation of unfolded proteins in the ER. Knockdown of the crt-1, pdi-2, or pdi-3 increased the crt-1 expression, whereas knockdown of the hsp-3 or hsp-4 did not have any effect on crt-1 expression, indicating the existence of complex compensatory networks to cope up with ER stress.
Related Concept Videos
Role of ER in the Secretory Pathway
Components of the secretory pathway
About a third of proteins synthesized in the cell are sorted via the secretory route. They shuffle between different compartments in membrane-bound vesicles until they reach their final destination. The main intracellular compartments involved...
ER Retrieval Pathway
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...
Protein Folding Quality Check in the RER
The Unfolded Protein Response
Export of Misfolded Proteins out of the ER
Regulation of the Unfolded Protein Response

