Fourier transform infrared microspectroscopy identifies protein propionylation in histone deacetylase inhibitor treated glioma cells

Abstract

Histone deacetylase inhibitors (HDIs) have attracted considerable attention as potential drug molecules in tumour biology. In order to optimise chemotherapy, it is important to understand the mechanisms of regulation of histone deacetylase (HDAC) enzymes and modifications brought by various HDIs. In the present study, we have employed Fourier transform infrared microspectroscopy (FT-IRMS) to evaluate modifications in cellular macromolecules subsequent to treatment with various HDIs. In addition to CH(3) (methyl) stretching bands at 2872 and 2960 cm(-1) , which arises due to acetylation, we also found major changes in bands at 2851 and 2922 cm(-1) , which originates from stretching vibrations of CH(2) (methylene) groups, in valproic acid treated cells. We further demonstrate that the changes in CH(2) stretching are concentration-dependent and also induced by several other HDIs. Recently, HDIs have been shown to induce propionylation besides acetylation [1]. Since propionylation involves CH(2) groups, we hypothesized that CH(2) vibrational frequency changes seen in HDI treated cells could arise due to propionylation. As verification, pre-treatment of cells with propionyl CoA synthetase inhibitor resulted in loss of CH(2) vibrational changes in histones, purified from valproic acid treated cells. This was further proved by western blot using propionyl-lysine specific antibody. Thus we demonstrate for the first time that propionylation could be monitored by studying CH(2) stretching using IR spectroscopy and further provide a platform for monitoring HDI induced multiple changes in cells.