Tracking Brain Palmitoylation Change: Predominance of Glial Change in a Mouse Model of Huntington’s Disease

Abstract

SUMMARY Protein palmitoylation, a reversible lipid modification of proteins, is widely used in the nervous system, with dysregulated palmitoylation being implicated in a variety of neurological disorders. Described below is ABE/SILAM, a new proteomic strategy that couples acyl-biotinyl exchange (ABE) purification of palmitoyl-proteins to whole animal stable isotope labeling (SILAM) to provide an accurate tracking of palmitoylation change within rodent disease models. As a first application, we have used ABE/SILAM to look at Huntington disease (HD), profiling palmitoylation change in two HD-relevant, mouse mutants – the transgenic HD model mouse YAC128 and the hypomorphic Hip14-gt mouse, which has sharply reduced expression for HIP14 (Dhhc17), a palmitoyl-transferase implicated in the HD disease process. Rather than mapping to the degenerating neurons themselves, the biggest disease changes instead map to astrocytes and oligodendrocytes, i.e. the supporting glial cells.

Trehalose rescues glial cell dysfunction in striatal cultures from HD R6/1 mice at early postnatal development

“…Furthermore, expression of mHTT in microglia is sufficient to produce an increase in pro-inflammatory gene expression and neurotoxic effect, making microglia to proliferate and turn in activated state, being closely linked the severity of the disease with the increase of microglia cell number. Inflammation is considered to appear early in the HD development and microglia responds to insults in the brain producing excess of inflammatory factors (Crotti et al, 2014;Kraft and Harry, 2011;Kraft et al, 2012;Tai et al, 2007;Wan et al, 2013). Our results showed an increase in microglia activation in HD vs WT, even further with epoxomicin treatment, but interestingly, trehalose balances the activated microglia profile.…”

“…Microglia proliferation and its activated state are closely linked to the severity of the disease. Inflammation is considered to appear early in the HD development and microglia responds to insults in the brain producing excess of inflammatory factors (Crotti et al, 2014;Kraft and Harry, 2011;Kraft et al, 2012;Tai et al, 2007;Wan et al, 2013). Our results showed an early response of microglia in HD cultures, including elevated numbers and activated morphological amoeboid phenotype, even more with epoxomicin treatment, but interestingly, trehalose equilibrates the activated microglia profile.…”

“…Trehalose has proven usefulness as a protectant against oxidative stress, as a chemical chaperone, autophagy inductor, and direct inhibitor of polyglutamine accumulation (Chen and Haddad, 2004;Ellis, 1987;Gonzalez-Parraga et al, 2003;Tanaka et al, 2004). Trehalose, due to these properties, has been shown to slow down the rate of protein aggregation and the resultant pathogenesis, by stabilizing the aggregation-prone model of proteins in neurodegenerative diseases Clabough, 2013;Ghavami et al, 2014;Perucho et al, 2012;Rodriguez-Navarro et al, 2010;Wan et al, 2013).…”

“…These huntingtin aggregates are expressed in neuronal and non-neuronal cells in the brain and several studies have documented a critical role of glia in the neuronal function (Crook and Housman, 2011;Chou et al, 2008;Shin et al, 2005;Zuccato et al, 2010). Glial cells play important roles in the development of neurodegenerative Molecular and Cellular Neuroscience 74 (2016) [128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145] diseases not only as a physical and structural support for neurons of nervous tissue (Bradford et al, 2009;Bradford et al, 2010b;Wan et al, 2013). Numerous investigations indicate that astrocytes and microglial cells participate actively in the modulation and transmission of nerve signals and production and release of neurotrophic factors and cytokines (Danbolt, 2001;Makar et al, 1994;Riederer et al, 1989;Voutsinos-Porche et al, 2003) and play crucial roles in adult CNS homeostasis regulation of neuronal environment.…”

Chemical Methods for Encoding and Decoding of Posttranslational Modifications

“…Specifically, free cysteines in a cell lysate are alkylated with N -ethylmaleimide, followed by treatment with hydroxylamine, which acts to cleave any palmitate thioesters revealing sulfhydryl groups that are then selectively modified with biotinylation reagents. Importantly, this method was used for the identification of palmitoylated proteins in yeast (Roth et al, 2006), mammalian cells (Ivaldi et al, 2012), malaria parasites (Jones et al, 2012), and mouse tissue (Wan et al, 2013). S-prenylation has also been investigated using alkyne derivatives of isoprenoids (Charron et al, 2011; DeGraw et al, 2010).…”