Polyamines Counteract Carbonate-Driven Proteasome Stalling in Alkaline Conditions.

Anna A Kudriaeva,Alexey A Belogurov,Alena N Kaminskaya,Vasiliy I Vladimirov,Petro Yu Barzilovich,George A Saratov

doi:10.3390/biom10121597

Abstract

Cancer cells tend to increase intracellular pH and, at the same time, are known to intensively produce and uptake polyamines such as spermine. Here, we show that various amines, including biogenic polyamines, boost the activity of proteasomes in a dose-dependent manner. Proteasome activity in the classical amine-containing buffers, such as 2-(N-morpholino)ethanesulfonic acid (MES), Tris, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), glycylglycine, bis-Tris propane, and bicine, has a skewed distribution with a maximum at pH of 7.0–8.0. The activity of proteasomes in buffers containing imidazole and bis-Tris is maintained almost on the same level, in the pH range of 6.5–8.5. The third type of activation is observed in buffers based on the amino acids arginine and ornithine, as well as the natural polyamines spermine and spermidine. Proteasome activity in these buffers is dramatically increased at pH values greater than 7.5. Anionic buffers such as phosphate or carbonate, in contrast, inhibit proteasome activity during alkalization. Importantly, supplementation of a carbonate–phosphate buffer with spermine counteracts carbonate-driven proteasome stalling in alkaline conditions, predicting an additional physiological role of polyamines in maintaining the metabolism and survival of cancer cells.

Highlights

Intracellular pH adjustment plays a crucial role in the metabolism and survival of the mammalian cell, as the activity of the majority of enzymes significantly depends on its value [1]
We investigate how the alkalization and increased concentration of polyamines may modulate the activity of proteasome, a part of the ubiquitin proteasome system (UPS), which degrades thousands of intracellular proteins
Activity of the 26S proteasome samples was inhibited in the presence of 0.02% SDS; both proteasomes were completely inhibited in presence of specific inhibitor MG132 (Figure 1c)

Summary

Introduction

Intracellular pH adjustment plays a crucial role in the metabolism and survival of the mammalian cell, as the activity of the majority of enzymes significantly depends on its value [1]. It has been known that cancer cells reorganize their metabolism in accord with the Warburg effect [4,5]. Together with genetic and epigenetic changes [6], shifts the metabolism of the cancer cells toward a more glycolytic phenotype [7], characterized by an exacerbated output of lactic acid [2]. A high-lactate concentration with an acidic intracellular pH, significantly enhances the survival of cancer cells under a lack of glucose. The high-lactate concentration, lactosis, with weak basic pH, has a pronounced effect on cell survival during glucose starvation [8]

Methods

Results

Conclusion