Loss of HDAC11 ameliorates clinical symptoms in a multiple sclerosis mouse model

In an animal model for multiple sclerosis, the absence of HDAC11 reduces clinical severity, spinal cord demyelination, and immune cell infiltration, suggesting that HDAC11 is a promising target for MS treatment.

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system (CNS). There is no known cure for MS, and currently available drugs for managing this disease are only effective early on and have many adverse side effects. Results from recent studies suggest that histone deacetylase (HDAC) inhibitors may be useful for the treatment of autoimmune and inflammatory diseases such as MS. However, the underlying mechanisms by which HDACs influence immune-mediated diseases such as MS are unclear. More importantly, the question of which specific HDAC(s) are suitable drug targets for the potential treatment of MS remains unanswered. Here, we investigate the functional role of HDAC11 in experimental autoimmune encephalomyelitis, a mouse model for MS. Our results indicate that the loss of HDAC11 in KO mice significantly reduces clinical severity and demyelination of the spinal cord in the post-acute phase of experimental autoimmune encephalomyelitis. The absence of HDAC11 leads to reduced immune cell infiltration into the CNS and decreased monocytes and myeloid DCs in the chronic progressive phase of the disease. Mechanistically, HDAC11 controls the expression of the pro-inflammatory chemokine C–C motif ligand 2 (CCL2) gene by enabling the binding of PU.1 transcription factor to the CCL2 promoter. Our results reveal a novel pathophysiological function for HDAC11 in CNS demyelinating diseases, and warrant further investigations into the potential use of HDAC11-specific inhibitors for the treatment of chronic progressive MS.

Programming and Regulation of Metabolic Homeostasis by HDAC11

Histone deacetylases (HDACs) are enzymes that regulate protein functions by catalyzing the removal of acetyl and acyl groups from lysine residues. They play pivotal roles in governing cell behaviors and are indispensable in numerous biological processes. HDAC11, the last identified and sole member of class IV HDACs, was reported over a decade ago. However, its physiological function remains poorly understood. Here, we report that HDAC11 knockout mice are resistant to high-fat diet-induced obesity and metabolic syndrome, suggesting that HDAC11 functions as a crucial metabolic regulator. Depletion of HDAC11 significantly enhanced insulin sensitivity and glucose tolerance, attenuated hypercholesterolemia, and decreased hepatosteatosis and liver damage. Mechanistically, HDAC11 deficiency boosts energy expenditure through promoting thermogenic capacity, which attributes to the elevation of uncoupling protein 1 (UCP1) expression and activity in brown adipose tissue. Moreover, loss of HDAC11 activates the adiponectin-AdipoR-AMPK pathway in the liver, which may contribute to a reversal in hepatosteatosis. Overall, our findings distinguish HDAC11 as a novel regulator of obesity, with potentially important implications for obesity-related disease treatment.

Histone deacetylase 10 regulates DNA mismatch repair and may involve the deacetylation of MutS homolog 2

MutS homolog 2 (MSH2) is an essential DNA mismatch repair (MMR) protein. It interacts with MSH6 or MSH3 to form the MutSα or MutSβ complex, respectively, which recognize base-base mispairs and insertions/deletions and initiate the repair process. Mutation or dysregulation of MSH2 causes genomic instability that can lead to cancer. MSH2 is acetylated at its C terminus, and histone deacetylase (HDAC6) deacetylates MSH2. However, whether other regions of MSH2 can be acetylated and whether other histone deacetylases (HDACs) and histone acetyltransferases (HATs) are involved in MSH2 deacetylation/acetylation is unknown. Here, we report that MSH2 can be acetylated at Lys-73 near the N terminus. Lys-73 is highly conserved across many species. Although several Class I and II HDACs interact with MSH2, HDAC10 is the major enzyme that deacetylates MSH2 at Lys-73. Histone acetyltransferase HBO1 might acetylate this residue. HDAC10 overexpression in HeLa cells stimulates cellular DNA MMR activity, whereas HDAC10 knockdown decreases DNA MMR activity. Thus, our study identifies an HDAC10-mediated regulatory mechanism controlling the DNA mismatch repair function of MSH2.

Abstract 1742: Potential roles of histone deacetylase 11 in cell cycle regulation and cancer

Histone deacetylases (HDACs) are enzymes that deacetylate lysine residues on histone and non-histone proteins. They regulate various cellular functions including transcriptional regulation, cell proliferation, apoptosis, and cellular metabolism. Broad spectrum HDAC inhibitors, including Vorinostat and Romidepsin, have been approved for cancer therapy, but their use is limited due to toxicity and side effects. A deeper understanding of the function of individual histone deacetylases could lead to the development of more specific and potentially more effective anti-cancer agents. In this context, Histone Deacetylase 11 (HDAC11) could be a potential target for anticancer therapeutics. HDAC11 is the most recently discovered Histone Deacetylase and, therefore, the least characterized among the 18 HDACs. Its expression is altered in various cancers and recent studies have suggested that HDAC11 might inhibit the activity and function of the DNA replication licensing factor Cdt1. To examine whether HDAC11 controls Cdt1-mediated cell cycle regulation, HDAC11 was overexpressed in human U87 glioblastoma cells. We found that overexpression of HDAC11 represses Cdt1 expression levels. Most importantly, we observed that HDAC11 overexpression promotes earlier cell entry into the G2/M phase of the cell cycle than non-HDAC11-overexpressed cells. Finally, we discovered that HDAC11 levels change throughout the cell cycle in a manner that is contrary to the Cdt1 expression levels. These results indicate that HDAC11 negatively regulates Cdt1, and uncover an important and previously unknown role of this enzyme in cell cycle regulation. Together, our findings suggest that development of drugs that target HDAC11 might be a viable strategy for overcoming cancers where this protein is overexpressed.

Citation Format: Thejal Srikumar, Elphine Telles, Edward Seto. Potential roles of histone deacetylase 11 in cell cycle regulation and cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1742. doi:10.1158/1538-7445.AM2013-1742

Modulation of cell cycle regulators by HDACs

Histone deacetylases (HDACs) catalyze the deacetylation of lysine residues on histones and non-histone proteins. HDACs have been shown to control the functions of key cell cycle proteins. Consistent with this, the overexpression of HDACs has been observed in multiple cancers, resulting in deregulation of the cell cycle and uncontrolled proliferation. This review focuses on the impact that HDACs have on cell cycle control through the deacetylation of proteins.

Filamin A stimulates cdc25C function and promotes entry into mitosis

The activity of the dual specificity phosphatase cdc25C is required for mitotic progression though the mechanisms by which cdc25C is activated prior to mitosis in human cells remain unclear. The data presented herein show that the actin binding protein Filamin A forms a complex with cdc25C in vivo and binds preferentially to the mitotic form of cdc25C. Co-expression of Filamin A with cdc25C results in an increase in PCC induced by cdc25C, while knocking down Filamin A expression reduces the levels of PCC induced by cdc25C overexpression. Further, only a Filamin A fragment that forms a complex with both cdc25C and cyclin B1 and retains the dimerization domain can stimulate the ability of cdc25C to induce PCC. These results suggest that Filamin A provides a platform for the assembly of the cyclin B1-cdk1- cdc25C complex resulting in cdk1 activation and mitotic progression.

A novel pocket in 14-3-3epsilon is required to mediate specific complex formation with cdc25C and to inhibit cell cycle progression upon activation of checkpoint pathways

Mitotic progression requires the activity of the dual specificity phosphatase, cdc25C. Cdc25C function is inhibited by complex formation with two 14-3-3 isoforms, 14-3-3epsilon and 14-3-3gamma. To understand the molecular basis of specific complex formation between 14-3-3 proteins and their ligands, chimeric 14-3-3 proteins were tested for their ability to form a complex with cdc25C in vivo. Specific complex formation between cdc25C and 14-3-3epsilon in vivo requires a phenylalanine residue at position 135 (F135) in 14-3-3epsilon. Mutation of this residue to the corresponding residue present in other 14-3-3 isoforms (F135V) leads to reduced binding to cdc25C and a decrease in the ability to inhibit cdc25C function in vivo. Similarly, F135V failed to rescue the incomplete S phase and the G2 DNA damage checkpoint defects observed in cells lacking 14-3-3epsilon. A comparative analysis of the 14-3-3 structures present in the database suggested that the F135 in 14-3-3epsilon was required to maintain the integrity of a pocket that might be involved in secondary interactions with cdc25C. These results suggest that the specificity of the 14-3-3 ligand interaction may be dependent on structural motifs present in the individual 14-3-3 isoforms.

The risk of inadvertent intrauterine device insertion in women carriers of endocervical Chlamydia trachomatis

The most important complication attributed to the use of intrauterine device (IUD) is pelvic inflammatory disease (PID), often associated with Neisseria or Chlamydia infection. Consequently, the IUD should not be inserted in women at risk of infection or with symptoms of endocervicitis. To evaluate the effectiveness of such a policy, a systematic investigation of Chlamydia and Neisseria was carried out among 407 contraceptive acceptors. Twenty-seven cases were positive for Chlamydia and none were positive for Neisseria. There were no statistical differences in the proportion of women with and without Chlamydia who had vulvovaginal or cervical signs or symptoms, although twice as many women had pain at pelvic exam in the Chlamydia-infected group. In 29 women in whom infection was clinically suspected, two were found to be infected with Chlamydia. IUD were not inserted in women suspected of having infection, but 19 of 327 IUD acceptors were subsequently found to have a positive Chlamydia test result. Two women returned with symptoms of PID and 17 were asymptomatic, but all were treated. PID was not suspected in any other subject. These results reinforce the need for careful selection of IUD acceptors and for thorough counseling for symptoms of PID and the need for immediate consultation.