Abstract
Metallothioneins (MTs) are known to protect cells against oxidative stress, especially providing protection against cadmium (Cd) toxicity in hepatocytes. There are various gene variants and pseudogenes for MTs; however, there is little understanding on the functions of those non-coding MT members that are known to be expressed as long non-coding RNAs (lncRNAs) nowadays. Different from most protein-coding MT members, MT1DP was here found that remarkably induced to provoke cytotoxicity in hepatocytes in response to Cd treatment. MT1DP exerted such a pro-apoptotic function in Cd-treated hepatocytes through interacting with two partners: RhoC and MT1H. On one hand, MT1DP interacted with RhoC protein to increase the latter’s stability by preventing lysosome-dependent protein degradation. Therefore, upon Cd stress, MT1DP/RhoC complex was quickly reinforced to activate RhoC-CCN1/2-AKT signaling and potentiate Ca2+ influx, leading to enhanced Cd uptake and elevated Cd toxicity. On the other hand, MT1H, a protein-coding member of the MT family with little known function, was found to quickly respond to Cd exposure along with MT1DP. Mechanistically, MT1H and MT1DP were uncovered to mutually protect each other through a reciprocal ceRNA mechanism, building up a positive feedback loop to enforce MT1DP-conducted signaling upon Cd exposure. Moreover, MT1DP was found to contribute much more to the activation of RhoC-CCN1/2-AKT signaling than MT1H. Considered together, we here unveiled a mystery whether a pseudogene within the MT family, MT1DP, has actual biological functions in regulating Cd-induced cellular defense. Our findings unearthed an important role of pseudogene MT1DP in calibrating the cellular machinery to switch the cellular defense to cytotoxicity through crosslinking an interplay between its two partners, namely MT1H and RhoC, under cadmium stress.
Highlights
Mammals have developed evolutionarily conserved intricate defense mechanisms against stress in response to toxic substances, such as antioxidant agents, detoxification enzymes, pro-survival signaling, autophagy and metal-binding proteins[1,2,3,4]
The induction of protein-coding members was confirmed at the protein levels, as evidenced by the western blot results (Fig. 1a), supporting of a critical role of MT1/2 against Cd toxicity[6]
To summarize, we uncovered a crucial role of an earlyresponse long noncoding RNAs (lncRNAs) MT1DP in chronologically enforcing cell death in hepatocytes under Cd stress
Summary
Mammals have developed evolutionarily conserved intricate defense mechanisms against stress in response to toxic substances, such as antioxidant agents, detoxification enzymes, pro-survival signaling, autophagy and metal-binding proteins[1,2,3,4]. The pivotal role of MTs in Cd detoxification has been established prominently due to Cd sequestration through their high-affinity binding inside cells, resulting in reduced Cd mass to prevent damage to cellular organelles[5, 6]. This mechanism is further verified by MT-transgenic mice, as increased. The interregulation among these members (e.g., synergism and antagonism) and their biological functions of non-coding pseudogenes ( known as long non-coding RNAs, lncRNAs) are still elusive
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
