Effects of Hydrogen Sulfide Donor GYY4137 on the Proteasome Pool of Colon Cancer Cells

Cancer cells are characterized by an increased level of metabolism and are highly dependent on the correct functioning of the processes that ensure homeostasis. Reactive sulfur species (RSS) are important molecular modulators of metabolic processes in both healthy and tumor cells. The effect of RSS and, in particular, H₂S, on key cellular systems, including the ubiquitin-proteasome system (UPS), which ensures the destruction of most intracellular proteins, has been shown. The main components of the UPS are proteasomes ‒ multisubunit protein complexes, within which protein proteolysis occurs. At the same time, data on the effect of H₂S directly on the pool of proteasomes in tumor cells are insufficient. Here, we studied the effect of incubation of SW620B8-mCherry colon adenocarcinoma cells expressing a fluorescently labeled proteasome subunit with 50, 100, and 200 µM of hydrogen sulfide donor GYY4137. The effect of the substance on the proteasome pool was assessed 6, 24, 48, and 72 h after administration. It was shown that the chymotrypsin-like and caspase-like proteasome activity decreases in cells incubated with 200 µM of the GYY4137 for 24 h. This coincided with an increase in the expression of proteasome subunit genes. In lysates of cells incubated with 200 µM GYY4137 for 48 h an increase in the content of the constitutive β5 subunit was observed. Against this background, the activity of proteasomes in cells levels off. Following prolonged incubation with GYY4137 (72h), an increase in the expression levels of some proteasome genes was also observed, though this did not have a significant effect on the activity and subunit composition of proteasomes. Thus, the data obtained indicate the modulation of proteasome activity by the hydrogen sulfide donor, as well as the effect of GYY4137 on the levels of transcription and translation of proteasome genes.