Depletion of transglutaminase 2 in neurons alters expression of extracellular matrix and signal transduction genes and compromises cell viability

Abstract

The protein transglutaminase 2 (TG2) has been implicated as a modulator of neuronal viability. TG2's role in mediating cell survival processes has been suggested to involve its ability to alter transcriptional events. The goal of this study was to examine the role of TG2 in neuronal survival and to begin to delineate the pathways it regulates. We show that depletion of TG2 significantly compromises the viability of neurons in the absence of any stressors. RNA sequencing revealed that depletion of TG2 dysregulated the expression of 86 genes with 59 of these being upregulated. The genes that were upregulated by TG2 knockdown were primarily involved in extracellular matrix function, cell signaling and cytoskeleton integrity pathways. Finally, depletion of TG2 significantly reduced neurite length. These findings suggest for the first time that TG2 plays a crucial role in mediating neuronal survival through its regulation of genes involved in neurite length and maintenance.

Nuclear transglutaminase 2 directly regulates expression of cathepsin S in rat cortical neurons

“…TG2 has been shown to regulate transcription in a number of cell types (Eckert et al., ), and our previous studies have shown that in neurons TG2 is a transcriptional regulator that primarily facilitates gene repression (Yunes‐Medina et al., ). The data presented here are the first to identify a specific DNA motif bound by TG2 and its location proximate to the gene Ctss .…”

“…Previous studies have shown that nuclear TG2 is primarily in the chromatin fraction (Lesort, Attanavanich, Zhang, & Johnson, ) and that in neurons TG2 supports cell viability with significantly increased nuclear levels in response to hypoxic stress (Filiano et al., , ; Yunes‐Medina et al., ). Although it is clear that TG2 mediates gene expression in neurons (Yunes‐Medina et al., ), it is not known whether these effects are direct or indirect. Therefore, we performed chromatin immunoprecipitation using neurons transduced with TG2‐V5.…”

“…An interesting outcome of TG2 knockdown in neurons is the significant decrease in neurite length and complexity. This attenuation of neurite length precedes the loss of neuronal viability, suggesting that it may be a contributing factor (Yunes‐Medina et al., ). This is intriguing given that Ctsk (cathepsin K; also known as cathepsin X) gene was also proximate to the TG2 precipitated DNA motif and upregulated when TG2 was knocked down.…”

“…Human TG2 cDNA was PCR amplified with a V5 tag at its C‐terminus (Gundemir, Colak, Feola, Blouin, & Johnson, ), followed by cloning into lentiviral expression vector FigB (a derivative of the FG12 vector from Addgene, Plasmid #14884, a gift from Dr C. Proschel) at the AgeI and EcoRI sites. Lentiviral vectors containing either shTG2 RNA or scrambled shRNA have been described previously (Yunes‐Medina, Paciorkowski, Nuzbrokh, & Johnson, ). HEK293TN cells were maintained in DMEM medium contains 10% Fetalclone‐II (FC‐II, Hyclone) at 37°C and 5% CO 2 .…”

Transglutaminase 2: Friend or foe? The discordant role in neurons and astrocytes

“…Overexpression of wild‐type TG2, but not the C277S mutant, resulted in spontaneous neurite outgrowth in SH‐SY5Y cells in low serum (Tucholski, Lesort, & Johnson, ), and differentiation of wild‐type SH‐SY5Y cells in the presence of a TG2 inhibitor resulted in significant inhibition of neurite outgrowth (Song et al, ). Further, in primary neurons, knocking down TG2 results in a pronounced decrease in neurite length (Yunes‐Medina, Paciorkowski, Nuzbrokh, & Johnson, ). Intriguingly, TG2 also appears to play a significant role in stabilization of axonal microtubules by catalyzing the incorporation of polyamines into tubulin.…”