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ATP13A2 (PARK9) is a late endolysosomal transporter that is genetically implicated in a spectrum of neurodegenerative disorders, including Kufor-Rakeb syndrome--a parkinsonism with dementia.sup.1--and early-onset Parkinson's disease.sup.2. ATP13A2 offers protection against genetic and environmental risk factors of Parkinson's disease, whereas loss of ATP13A2 compromises lysosomes.sup.3. However, the transport function of ATP13A2 in lysosomes remains unclear. Here we establish ATP13A2 as a lysosomal polyamine exporter that shows the highest affinity for spermine among the polyamines examined. Polyamines stimulate the activity of purified ATP13A2, whereas ATP13A2 mutants that are implicated in disease are functionally impaired to a degree that correlates with the disease phenotype. ATP13A2 promotes the cellular uptake of polyamines by endocytosis and transports them into the cytosol, highlighting a role for endolysosomes in the uptake of polyamines into cells. At high concentrations polyamines induce cell toxicity, which is exacerbated by ATP13A2 loss due to lysosomal dysfunction, lysosomal rupture and cathepsin B activation. This phenotype is recapitulated in neurons and nematodes with impaired expression of ATP13A2 or its orthologues. We present defective lysosomal polyamine export as a mechanism for lysosome-dependent cell death that may be implicated in neurodegeneration, and shed light on the molecular identity of the mammalian polyamine transport system. The lysosomal polyamine transporter ATP13A2 controls the cellular polyamine content, and impaired lysosomal polyamine export represents a lysosome-dependent cell death pathway that may be implicated in ATP13A2-associated neurodegeneration., Author(s): Sarah van Veen [sup.1] , Shaun Martin [sup.1] , Chris Van den Haute [sup.2] [sup.3] , Veronick Benoy [sup.1] , Joseph Lyons [sup.4] , Roeland Vanhoutte [sup.5] , Jan [...]

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disorder due to selective loss of motor neurons (MNs). Mutations in the fused in sarcoma (FUS) gene can cause both juvenile and late onset ALS. We generated and characterized induced pluripotent stem cells (iPSCs) from ALS patients with different FUS mutations, as well as from healthy controls. Patient-derived MNs show typical cytoplasmic FUS pathology, hypoexcitability, as well as progressive axonal transport defects. Axonal transport defects are rescued by CRISPR/Cas9-mediated genetic correction of the FUS mutation in patient-derived iPSCs. Moreover, these defects are reproduced by expressing mutant FUS in human embryonic stem cells (hESCs), whereas knockdown of endogenous FUS has no effect, confirming that these pathological changes are mutant FUS dependent. Pharmacological inhibition as well as genetic silencing of histone deacetylase 6 (HDAC6) increase α-tubulin acetylation, endoplasmic reticulum (ER)–mitochondrial overlay, and restore the axonal transport defects in patient-derived MNs. [ABSTRACT FROM AUTHOR]

Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Herein, the synthesis of ten new benzohydroxamic acids, constructed by employing the tetrahydrobenzothiazepine core as a privileged pharmacophoric unit, is described. This is the first report on the synthesis and isolation of octahydrodibenzothiazepines and octahydro-6 H-benzocycloheptathiazepines, which were then used to develop a new class of HDAC6 inhibitors. Evaluations of their HDAC-inhibiting activity resulted in the identification of cis- N-(4-hydroxycarbamoylbenzyl)-1,2,3,4,4 a,5,11,11 a-octahydrodibenzo[ b, e][1,4]thiazepine-10,10-dioxide and cis- N-(4-hydroxycarbamoylbenzyl)-7-trifluoromethyl-1,2,3,4,4 a,5,11,11 a-octahydrodibenzo[ b, e][1,4]thiazepine-10,10-dioxide as highly potent and selective HDAC6 inhibitors with activity in the low nanomolar range, which also show excellent selectivity on the enzymatic and cellular levels. Furthermore, four promising inhibitors were subjected to an Ames fluctuation assay, which revealed no mutagenic effects associated with these structures. [ABSTRACT FROM AUTHOR]

Calcium ions (Ca 2+ ) are prominent cell signaling effectors that regulate a wide variety of cellular processes. Among the different players in Ca 2+ homeostasis, primary active Ca 2+ transporters are responsible for keeping low basal Ca 2+ levels in the cytosol while establishing steep Ca 2+ gradients across intracellular membranes or the plasma membrane. This review summarizes our current knowledge on the three types of primary active Ca 2+ -ATPases: the sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA) pumps, the secretory pathway Ca 2+ - ATPase (SPCA) isoforms, and the plasma membrane Ca 2+ -ATPase (PMCA) Ca 2+ -transporters. We first discuss the Ca 2+ transport mechanism of SERCA1a, which serves as a reference to describe the Ca 2+ transport of other Ca 2+ pumps. We further highlight the common and unique features of each isoform and review their structure-function relationship, expression pattern, regulatory mechanisms, and specific physiological roles. Finally, we discuss the increasing genetic and in vivo evidence that links the dysfunction of specific Ca 2+ -ATPase isoforms to a broad range of human pathologies, and highlight emerging therapeutic strategies that target Ca 2+ pumps., (Copyright © 2020 Cold Spring Harbor Laboratory Press; all rights reserved.)

Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Herein, the synthesis of ten new benzohydroxamic acids, constructed by employing the tetrahydrobenzothiazepine core as a privileged pharmacophoric unit, is described. This is the first report on the synthesis and isolation of octahydrodibenzothiazepines and octahydro-6H-benzocycloheptathiazepines, which were then used to develop a new class of HDAC6 inhibitors. Evaluations of their HDAC-inhibiting activity resulted in the identification of cis-N-(4-hydroxycarbamoylbenzyl)-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide and cis-N-(4-hydroxycarbamoylbenzyl)-7-trifluoromethyl-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide as highly potent and selective HDAC6 inhibitors with activity in the low nanomolar range, which also show excellent selectivity on the enzymatic and cellular levels. Furthermore, four promising inhibitors were subjected to an Ames fluctuation assay, which revealed no mutagenic effects associated with these structures., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Charcot-Marie-Tooth (CMT) disease is a disorder of the peripheral nervous system where progressive degeneration of motor and sensory nerves leads to motor problems and sensory loss and for which no pharmacological treatment is available. Recently, it has been shown in a model for the axonal form of CMT that histone deacetylase 6 (HDAC6) can serve as a target for the development of a pharmacological therapy. Therefore, we aimed at developing new selective and activity-specific HDAC6 inhibitors with improved biochemical properties. By utilizing a bicyclic cap as the structural scaffold from which to build upon, we developed several analogues that showed improved potency compared to tubastatin A while maintaining excellent selectivity compared to HDAC1. Further screening in N2a cells examining both the acetylation of α-tubulin and histones narrowed down the library of compounds to three potent and selective HDAC6 inhibitors. In mutant HSPB1-expressing DRG neurons, serving as an in vitro model for CMT2, these inhibitors were able to restore the mitochondrial axonal transport deficits. Combining structure-based development of HDAC6 inhibitors, screening in N2a cells and in a neuronal model for CMT2F, and preliminary ADMET and pharmacokinetic profiles, resulted in the selection of compound 23d that possesses improved biochemical, functional, and druglike properties compared to tubastatin A.

Charcot-Marie-Tooth disease is the most common inherited disorder of the peripheral nervous system. The disease is characterized by a progressive muscle weakness and atrophy, sensory loss, foot (and hand) deformities and steppage gait. While many of the genes associated with axonal CMT have been identified, to date it is unknown which mechanism(s) causes the disease. However, genetic findings indicate that the underlying mechanisms mainly converge to the axonal cytoskeleton. In this review, we will summarize the evidence for this pathogenic convergence. Furthermore, recent work with new transgenic mouse models has led to the identification of histone deacetylase 6 as a potential therapeutic target for inherited peripheral neuropathies. This enzyme deacetylates microtubules and plays a crucial role in the regulation of axonal transport. These findings offer new perspectives for a potential therapy to treat axonal Charcot-Marie-Tooth disease and other neurodegenerative disorders characterized by axonal transport defects., (Copyright © 2012 Elsevier Ltd. All rights reserved.)