MRP-L21 inhibitors target various aspects of mitochondrial function, indirectly affecting the activity of the mitochondrial ribosomal protein L21 (MRP-L21). Compounds such as Omeprazole and Valinomycin disrupt the mitochondrial membrane potential, which is crucial for ATP production. Since MRP-L21 function within the mitochondrial ribosome is an energy-dependent process, a decrease in ATP synthesis can inhibit the activity of MRP-L21. Similarly, Bortezomib induces proteotoxic stress, which can result in the misfolding of mitochondrial proteins, including MRP-L21, affecting its integration into the mitochondrial ribosome.
Other inhibitors like Metformin, Rapamycin, and Chloroquine exert their effects through pathways that indirectly impact mitochondrial biogenesis and function. Metformin, through the activation of AMPK, can lead to reduced translation of mitochondrial-encoded proteins, consequently diminishing the role of MRP-L21 in the mitochondrial ribosome complex. Rapamycin's inhibition of the mTOR pathway can downregulate mitochondrial biogenesis, affecting the incorporation of MRP-L21 into mitochondrial ribosomes. Chloroquine, by interfering with autophagy, can lead to the accumulation of damaged mitochondria, indirectly inhibiting the function of MRP-L21 by impairing the organelle where it functions. Inhibition of key enzymes in the electron transport chain, such as with Rotenone and Antimycin A, leads to a decrease in ATP synthesis, which is vital for the assembly and operation of MRP-L21 within the mitochondrial ribosome. Additionally, Tetracycline directly binds to ribosomal subunits, potentially inhibiting the mitochondrial ribosome and thereby the function of MRP-L21 in protein synthesis.