Histone deacetylase inhibitors induce expression of chromosomally tagged variant-specific surface protein genes in Giardia lamblia

Abstract

Objective: RNA interference and miRNA mediated mechanisms have been proposed to explain the expression of a specific variant of VSP at a time on the surface of Giardia lamblia. Recently, epigenetic mechanisms involving histone acetylations have been proposed to explain the process of vsp gene switching in Giardia lamblia. However, due to the limited availability of specific antibodies for all the vsp variants present in the genome, it was difficult to monitor vsp gene switching. In this study, we have used an endogenous tagging method to tag specific vsp genes vsp1267 and vsp9B10A with a sequence encoding hemagglutinin (HA) epitope at the 3′end of the coding sequences without altering the 5′ upstream elements. With this method, we have monitored the expression of the tagged vsp genes in cells treated with histone deacetylase inhibitors using RT-PCR. Results:Our results show that vsp1267-3XHA can be induced by treatment with sodium 4-phenylbutyrate, M344 and splitomicin but not by apicidin and Trichostatin A, while vsp9B10A-3XHA expression can be induced by Trichostatin A and splitomicin but not by sodium 4-phenylbutyrate, M344 and apicidin. The induced expression of these variants was not due to growth inhibition. These results support the role of histone acetylations in vsp expression.

Sirtuin GdSir2.4 participates in the regulation of rRNA transcription in the Giardia duodenalis parasite

“…TSA inhibits the activity of NAD+‐independent HDACs by interacting with its catalytic site through its hydroxamate motif, thus preventing the zinc cofactor from binding properly and mediating amide cleavage (Vanhaecke et al., 2004). TSA has been shown to promote antigenic variation in Giardia (Carranza et al., 2016; Orozco & Garlapati, 2020). The only NAD+‐independent HDAC identified in Giardia (GL50803_3281) has residues in the catalytic pocket that coordinate the binding of zinc and are in contact with TSA (Sonda et al., 2010).…”

Ultrastructural Alterations of the Human Pathogen Giardia intestinalis after Drug Treatment

“…This process plays a regulatory role in the parasite’s genome, with the activity of histone acetyltransferase and histone deacetylase enzymes governing it. The levels of acetylation on histones are associated with the control of gene expression during the differentiation of trophozoites into cysts and the regulation of transcription and expression of genes encoding specific variant surface proteins (VSPs) [ 81 , 82 , 83 ].…”

“…Through drug repositioning efforts, several studies have demonstrated the potential of these compounds against protozoan parasites, including G. intestinalis . For instance, Trichostatin A, tubastatine A, and nicotinamide have been shown to inhibit trophozoite proliferation [ 82 , 83 , 85 ]. Additionally, novel HDAC inhibitors named KH-TFMDI, a member of the 3-arylideneindolin-2-one family, and KV-46, a 4-[(10H-phenothiazin-10-yl)methyl]-N-hydroxy benzamide, exhibited the ability to modulate G. intestinalis growth, with IC50 values below 1 μM ( Figure 17 ).…”

Giardia VSPAS7 protein attenuates Giardia intestinalis-induced host macrophage pyroptosis

“…Variant-specific surface proteins cover Giardia 's trophozoite surface (including flagella and ventral disc) and belong to a family of related and highly unusual proteins. There are approximately 200 VSPs in Giardia [ 4 ], but just one VSP is ever expressed at any one time on a single trophozoite surface [ 6 ], while multiple VSPs are expressed simultaneously during cyst formation [ 7 ]. This protein family is typically characterized by a varied N-terminal region, a conserved transmembrane region and a CRGKA intracellular tail [ 8 ].…”