Artemin as an Efficient Molecular Chaperone

Abstract

Artemin is an abundant thermostable protein in Artemia encysted embryos under stress. It is considered as a stress protein, as its highly regulated expression is associated with stress resistance in this crustacea. In the present study, artemin has been shown to be a potent molecular chaperone with high efficacy. Artemin is capable of inhibiting the chemical aggregation of proteins such as carbonic anhydrase (CA) and horseradish peroxidase (HRP) at unique molar ratios of chaperone to substrates (1:40 and 1:26 for CA and HRP, respectively). Furthermore, it can also enhance refolding yield of these substrates by nearly 50%. The refolding promotion of CA is checked and verified through a sensitive fluorimetric technique. Based on these experiments, artemin showed higher chaperone activity than other chaperones. The evaluation of artemin surface using ANS showed it to be highly hydrophobic, probably resulting in its high efficacy. These results suggest that artemin can be considered a novel low molecular weight chaperone.

Artemin, a Diapause-Specific Chaperone, Contributes to the Stress Tolerance of Artemia Cysts and Influences Their Release from Females

“…Artemin is a heat-tolerant, cysteine-enriched, diapause-specific protein found in A. franciscana cysts that protects other proteins from stress-induced denaturation in vitro (Chen et al, 2007;Hu et al, 2011;Shirzad et al, 2011;Shahangian et al, 2011) and binds non-polyadenylated RNA when heated (Warner et al, 2004). Assuming that artemin and p26 transcripts are equally available within the cytoplasm for translation, then artemin mRNA is translated less efficiently than p26 mRNA, a conclusion occasioned by the twofold difference in the amount of mRNAs but similar abundance of their protein products.…”

“…Artemin, an abundant, ATP-independent, diapause-specific molecular chaperone shown to protect transfected mammalian cells from stress and prevent protein denaturation in vitro, is a ferritin homolog (Chen et al, 2003;Warner et al, 2004;Chen et al, 2007;Hu et al, 2011;Shirzad et al, 2011;Shahangian et al, 2011). Artemin assembles oligomers of ~600-700 kDa formed from 24 monomers, each ~26 kDa (De Graaf et al, 1990;Chen et al, 2007;Clegg, 2011;Hu et al, 2011).…”

Stress tolerance during diapause and quiescence of the brine shrimp, Artemia

“…Most artemin mRNA is gone from early cyst-derived nauplii (Chen et al 2003) but when the protein disappears is unknown. Artemin is extremely stable, enduring extended cyst storage, years of anoxia, and heating in vitro at 70°C which causes binding of non-polyadenylated RNA (Warner et al 2004;Shahangian et al 2011). Structural stability and the correspondence between abundance and elevated stress resistance imply that artemin protects Artemia cysts, a proposition proven by reduced tolerance to desiccation and freezing after knockdown of artemin (King et al 2014).…”

“…Purified artemin prevents heat-induced denaturation of other proteins in the absence of added ATP, an activity shared by ferritin (Chen et al 2007;Hu et al 2011;Shahangian et al 2011). The heat resistance of transformed bacteria synthesizing artemin is enhanced (Rasti et al 2009), and stably transfected mammalian cells containing artemin have increased tolerance to thermal and oxidative stress (Chen et al 2007).…”

“…For example, changing C172 maximally reduces chaperone activity but has minimal influence on stability, whereas modifying C22 and C61 has the greatest impact on stability and the least on chaperoning. Cysteine substitutions, along with 1-aniline-8-naphthalene-sulfonate (ANS) reactivity, indicate that surface hydrophobicity contributes to artemin chaperoning (Hu et al 2011;Shahangian et al 2011).…”