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The ability of cells to store and rapidly mobilize energy reserves in response to nutrient availability is essential for survival. Breakdown of carbon stores produces acetyl-coenzyme-A (acetyl-CoA), which fuels various metabolic pathways and is also the acyl donor for protein lysine acetylation. Notably, histone acetylation is sensitive to acetyl-CoA availability and nutrient replete conditions induce a substantial accumulation of acetylation on histones. Deacetylation releases acetate, which can be recycled to acetyl-CoA, suggesting that deacetylation could be mobilized as an acetyl-CoA source to feed downstream metabolic processes under nutrient depletion. While the notion of histones as a metabolic reservoir has been frequently proposed, experimental evidence has been lacking. Therefore, to test this concept directly, we developed an experimental system to trace deacetylation-derived acetate and its incorporation into acetyl-CoA, using13C2-acetate in ATP citrate lyase-deficient fibroblasts (Acly-/-MEFs), which are primarily dependent on acetate for protein acetylation. We find that dynamic protein deacetylation inAcly-/-MEFs contributes carbons to acetyl-CoA and proximal downstream metabolites. However, there is no significant effect on acyl-CoA pool sizes, and even at maximal acetylation, deacetylation transiently supplies approximately 9% of cellular acetyl-CoA. Together, our data reveal that although protein acetylation is dynamic and sensitive to nutrient availability, its potential for maintaining cellular acetyl-CoA-dependent metabolic pathways is limited compared to cellular demand.

Puromycin is an amino nucleoside that inhibits protein synthesis by interrupting elongation of nascent peptide chains. It is a commonly used selection antibiotic in molecular biology research via engineered expression of a puromycin resistance transgene. The enzyme puromycin acetyl transferase (pac) or PuroR inactivates puromycin by N-acetylating its reactive amino group. Puromycin acetylation by pac requires the central metabolite and acetyl group donor acetyl-CoA as a substrate. We found that puromycin treatment exacerbates sensitivity of cancer cells to knockdown of pantothenate kinases, the proteins that catalyze the rate-limiting step of de novo coenzyme A production in cells. Mechanistically, we found that ablation of PANKs together with puromycin depletes acetyl-CoA levels, in a manner modulated by the dose of puromycin. Our findings provide a note of caution and context in the use of puromycin for metabolism research in that interference with the major acyl donor used for inactivating biotransformation may exacerbate toxicity under selection. Broadly, our findings also invite studies to explore how targeting CoA and acetyl-CoA synthesis may be exploited to enhance cytotoxic effects of cancer drugs that undergo acetylation.

Prenatal testosterone (T)-treated female sheep exhibit an enhanced inflammatory and oxidative stress state in the visceral adipose tissue (VAT) but not in the subcutaneous (SAT), while surprisingly maintaining insulin sensitivity in both depots. In adult sheep, adipose tissue is predominantly composed of white adipocytes which favor lipid storage. Brown/beige adipocytes that make up the brown adipose tissue (BAT) favor lipid utilization due to thermogenic uncoupled protein 1 expression and are interspersed amidst white adipocytes, more so in epicardiac (ECAT) and perirenal (PRAT) depots. The impact of prenatal T-treatment on ECAT and PRAT depots are unknown. As BAT imparts a metabolically healthy phenotype, the depot-specific impact of prenatal T-treatment on inflammation, oxidative stress, differentiation and insulin sensitivity could be dictated by the distribution of brown adipocytes. This hypothesis was tested by assessing markers of oxidative stress, inflammation, adipocyte differentiation, fibrosis and thermogenesis in adipose depots from control and prenatal T (100 mg T propionate twice a week from days 30–90 of gestation) -treated female sheep at 21 months of age. Our results show prenatal T-treatment induces depot-specific changes in inflammation, oxidative stress state, collagen accumulation, and differentiation with changes being more pronounced in the VAT. Prenatal T-treatment also increased thermogenic gene expression in all depots indicative of increased browning with effects being more prominent in VAT and SAT. Considering that inflammatory and oxidative stress are also elevated, the increased brown adipocyte distribution is likely a compensatory response to maintain insulin sensitivity and function of organs in the proximity of respective depots.

Gigaxonin, the protein product of the Giant axonal neuropathy (GAN) gene, is a E3 ubiquitin ligase involved in neural cell and fibroblast intermediate filament processing. We have previously shown that Gigaxonin interacts with p16 in cisplatin-mediated ubiquitination of NF-κB. We analyzed cervical and head and neck cancer cell lines and primary tumors and have found exon 8 c.1293C>T single nucleotide polymorphism (SNP) to occur in both HPV positive and negative tumor cells lines and primary tumors. The prevalence of this SNP in the tumor samples was double that of the normal population (47.25% vs. 22%) and there was no relationship to HPV status. Cell lines containing the SNP showed higher expression of gigaxonin, and an inverse relationship to in vitro tumor cell line growth and cisplatin sensitivity. There was a direct relationship between the expression of gigaxonin and e-cadherin and inverse relationship to the expression of twist, snail and n-cadherin. CRISPR-Cas9 mediated conversion of T to C allele in gigaxonin overexpressing cervical cancer cell line ME 180 resulted in decreased gigaxonin expression accompanied by increased expression of twist, and snail and increased in vitro cell growth. Re-expression of gigaxonin in the CRISPR-Cas9 clone with a plasmid gigaxonin cDNA construct resulted in decreased expression of twist pointing to gigaxonin mediated downregulation of the EMT marker. We therefore hypothesize that GAN, associated with the neurodegenerative disease, is also a human tumor cell growth suppressor gene. Citation Format: Mysore S. Veena, Daniel Sanghoon Shin, Chan Jeong, Jenna R. Chatoff, Natarajan Venkatesan, Saroj K. Basak, David Gray, Sharon P. Wilczynski, Sharon P. Wilczynski, Steven J. Gray, Donald B. Kohn, Marilene B. Wang, Eri S. Srivatsan. Inverse relationship between Giant Axonal Neuropathy gene expression and EMT in human tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5986.

Gigaxonin is the protein product of Giant Axonal Neuropathy (GAN) gene and is involved in the processing of intermediate filaments of neural cells and vimentin fibers in fibroblasts. We have shown earlier that gigaxonin is associated with p16 in NFkB ubiquitination of cisplatin sensitive tumor cells. Our studies have shown that there is a direct relationship between the presence of exon 8 SNP (C>T) and expression of giagxonin in cancer cell lines. We have also seen an inverse relationship between exon 8 SNP and tumor recurrence and metastasis. RNA-seq studies of cancer cell lines and primary tumors have shown a direct relationship in the expression of gigaxonin to the expression of e-cadherin and inverse relationship to the expression of Vimentin and Zeb1. Immunohistochemical (IHC) studies of primary head and neck cancers have confirmed the inverse relationship between e-cadherin and vimentin. We hypothesize therefore that gigaxonin is involved in the ubiquitination of vimentin and cancer stem cell markers such as zeb1 resulting in the chemo sensitization of human tumor cells. Citation Format: Albert Ko, Natarajan Venkatesan, Jenna Chatoff, Marco Morselli, Gregory Fishbein, Pascale Bomont, Matteo Pellegrini, Marilene Wang, Eri Srivatsan. GAN gene exon 8 SNP is related to gigaxonin expression and increased expression of e-cadherin in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5505.

Gigaxonin, a product of the Giant Axonal Neuropathy (GAN) gene located on chromosome 16, is involved in intermediate filament processing of neural cells and vimentin fibers in fibroblasts. Previous studies have shown an interaction between p16 and gigaxonin in cisplatin mediated ubiquitination of NFkB. Genomic studies have indicated higher frequency (44.25%) of exon 8 single nucleotide polymorphism (SNP) (c.1293 C>T) of gigaxonin in the individuals of Caucasian population compared to normal population (22%). The polymorphism frequency is much lower in individuals of other ethnicities. To determine the relationship to tumors, we analyzed exon 8 polymorphism in HPV positive and negative cervical and head and tumors. Our studies showed a 47.25% polymorphic frequency in these tumors. There was no relationship between the presence of polypmorphism and HPV status. However, there was an inverse relationship between polymorphism and tumor recurrence. Our studies have further shown higher expression of gigaxonin protein in cancer cell lines containing the polymorphic T allele. Growth assays in vitro and in soft agar have shown a direct relationship between the presence of the T allele and slower cell line growth. Our results therefore indicate that in addition to p16 expression, exon 8 SNP could also serve as a diagnostic marker of chemo sensitivity in human tumors. Citation Format: Eri S. Srivatsan, Kimberly J. Hwang, Albert Ko, Jenna R. Chatoff, Saroj K. Basak, Natarajan Venkatesan, Fernando Palma-Diaz, Michael S. Lewis, Pascale Bomont, Marilene B. Wang. Inverse relationship between exon 8 single nucleotide polymorphism (c.1293 C>T) of gigaxonin and human tumor cell growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4457. doi:10.1158/1538-7445.AM2017-4457