Human pantothenate kinase 4 is a pseudo-pantothenate kinase

A comprehensive view of muscle glucose uptake: regulation by insulin, contractile activity, and exercise

Skeletal muscle is the main site of glucose deposition in the body during meals and the major glucose utilizer during physical activity. Although in both instances the supply of glucose from the circulation to the muscle is of paramount importance, in most conditions the rate-limiting step in glucose uptake, storage, and utilization is the transport of glucose across the muscle cell membrane. This step is dependent upon the translocation of the insulin- and contraction-responsive glucose transporter GLUT4 from intracellular storage sites to the sarcolemma and T tubules. Here, we first analyze how glucose can traverse the capillary wall into the muscle interstitial space. We then review the molecular processes that regulate GLUT4 translocation in response to insulin and muscle contractions and the methodologies utilized to unravel them. We further discuss how physical activity and inactivity, respectively, lead to increased and decreased insulin action in muscle and touch upon sex differences in glucose metabolism. Although many key processes regulating glucose uptake in muscle are known, the advent of newer and bioinformatics tools has revealed further molecular signaling processes reaching a staggering level of complexity. Much of this molecular mapping has emerged from cellular and animal studies and more recently from application of a variety of -omics in human tissues. In the future, it will be imperative to validate the translatability of results drawn from experimental systems to human physiology.

The two faces of coenzyme A in cellular biology

Coenzyme A (CoA) is an essential cofactor present in all living cells, which plays critical roles in diverse biochemical processes, including cellular metabolism, signal transduction, regulation of gene expression, and the antioxidant response. This review summarizes current knowledge on the role of CoA and its metabolically active thioesters in promoting cellular growth and proliferation (pro-growth) and discusses emerging research on CoA's antioxidant properties that enhance cell survival (pro-survival).

Augmented Acyl-CoA Biosynthesis Promotes Resistance to TEAD Palmitoylation Site Inhibition

Activation of the YAP-TEAD transcriptional complex drives the growth of several cancer types and is a key resistance mechanism to targeted therapies. Accordingly, a host of pharmacological inhibitors to TEAD family paralogs have been developed, yet little is known as to the resistance mechanisms that might arise against this emerging therapeutic class. Here, we report that genetic augmentation of de novo coenzyme A biosynthesis desensitizes YAP-dependent cancer cells to treatment with TEAD inhibitors, an effect driven by increased levels of palmitoyl-CoA that outcompete drug for engagement of the lipid-binding pocket. This work uncovers a potential therapeutic resistance mechanism to TEAD palmitoylation site inhibition with implications for future combinatorial treatments in the clinic.

Pantothenate kinase 4 controls skeletal muscle substrate metabolism

Metabolic flexibility in skeletal muscle is essential for maintaining healthy glucose and lipid metabolism, and its dysfunction is closely linked to metabolic diseases. Exercise enhances metabolic flexibility, making it an important tool for discovering mechanisms that promote metabolic health. Here we show that pantothenate kinase 4 (PanK4) is a new conserved exercise target with high abundance in muscle. Muscle-specific deletion of PanK4 impairs fatty acid oxidation which is related to higher intramuscular acetyl-CoA and malonyl-CoA levels. Elevated acetyl-CoA levels persist regardless of feeding state and are associated with whole-body glucose intolerance, reduced insulin-stimulated glucose uptake in glycolytic muscle, and impaired glucose uptake during exercise. Conversely, increasing PanK4 levels in glycolytic muscle lowers acetyl-CoA and enhances glucose uptake. Our findings highlight PanK4 as an important regulator of acetyl-CoA levels, playing a key role in both muscle lipid and glucose metabolism.

Identification of a depupylation regulator for an essential enzyme in Mycobacterium tuberculosis

In Mycobacterium tuberculosis (Mtb), proteins that are posttranslationally modified with a prokaryotic ubiquitin-like protein (Pup) can be degraded by bacterial proteasomes. A single Pup-ligase and depupylase shape the pupylome, but the mechanisms regulating their substrate specificity are incompletely understood. Here, we identified a depupylation regulator, a protein called CoaX, through its copurification with the depupylase Dop. CoaX is a pseudopantothenate kinase that showed evidence of binding to pantothenate, an essential nutrient Mtb synthesizes, but not its phosphorylation. In a ∆coaX mutant, pantothenate synthesis enzymes including PanB, a substrate of the Pup-proteasome system (PPS), were more abundant than in the parental strain. In vitro, CoaX specifically accelerated depupylation of Pup~PanB, while addition of pantothenate inhibited this reaction. In culture, media supplementation with pantothenate decreased PanB levels, which required CoaX. Collectively, we propose CoaX regulates PanB abundance in response to pantothenate levels by modulating its vulnerability to proteolysis by Mtb proteasomes.

The iron maiden: Oligodendroglial metabolic dysfunction in multiple sclerosis and mitochondrial signaling

Multiple sclerosis (MS) is an autoimmune disease, governed by oligodendrocyte (OL) dystrophy and central nervous system (CNS) demyelination manifesting variable neurological impairments. Mitochondrial mechanisms may drive myelin biogenesis maintaining the axo-glial unit according to dynamic requisite demands imposed by the axons they ensheath. The promotion of OL maturation and myelination by actively transporting thyroid hormone (TH) into the CNS and thereby facilitating key transcriptional and metabolic pathways that regulate myelin biogenesis is fundamental to sustain the profound energy demands at each axo-glial interface. Deficits in regulatory functions exerted through TH for these physiological roles to be orchestrated by mature OLs, can occur in genetic and acquired myelin disorders, whereby mitochondrial efficiency and eventual dysfunction can lead to profound oligodendrocytopathy, demyelination and neurodegenerative sequelae. TH-dependent transcriptional and metabolic pathways can be dysregulated during acute and chronic MS lesion activity depriving OLs from critical acetyl-CoA biochemical mechanisms governing myelin lipid biosynthesis and at the same time altering the generation of iron metabolism that may drive ferroptotic mechanisms, leading to advancing neurodegeneration.

Decreased PANK1 expression in kidney renal clear cell carcinoma: impact on cell apoptosis, invasion, migration, and epithelial-mesenchymal transition

OBJECTIVE

To investigate pantothenate kinases 1 (PANK1) expression in kidney renal clear cell carcinoma (KIRC) tissues, analyze its correlation with clinicopathological features and prognosis, and explore its impact on invasion, migration, and apoptosis in KIRC cells.

METHODS

GEPIA (gene expression profiling interactive analysis), UALCAN and LinkedOmics, were employed to analyze PANK1 expression in KIRC tissues and its correlation with clinical characteristics. Comparative analyses were performed between KIRC (Caki-1 and 786-O) and noncancerous renal cells (HK-2 and RPTEC). Transfection with PANK1 activation particles was conducted, followed by Wound healing, Transwell assay, Annexin V-fluorescein isothiocyanate/propidium iodide (Annexin V-FITC/PI) staining, quantitative reverse-transcription polymerase chain reaction (qRT-PCR), and Western blotting.

RESULTS

PANK1 was down-regulated in KIRC tissues and cells compared to normal tissues and noncancerous cells. Correlation analyses linked PANK1 expression with clinicopathological features in KIRC, with high PANK1 expression associated with a favorable outcome. High PANK1 expression correlated positively with E-cadherin (CDH1), tight junction protein 1 (TJP1), Fas cell surface death receptor (FAS), caspase-8 (CASP8), and CASP9, while showing a negative correlation with vimentin (VIM), snail family transcriptional repressor 1 (SNAIL1), twist family BHLH transcription factor 1 (TWIST1), and TWIST2. PANK1 overexpression increased CDH1, TJP1, FAS, CASP8, and CASP9 while downregulating SNAIL1, VIM, TWIST1, and TWIST2, inhibiting invasion and migration, and promoting apoptosis in KIRC cells.

CONCLUSION

PANK1 down-regulation in KIRC tissues correlated with clinicopathological features and prognosis. Its overexpression modulated epithelial-mesenchymal transition (EMT)-related gene, inhibited invasion, promoted apoptosis in KIRC cells, highlighting its role in disease progression and therapeutic potential.

Coenzyme A biosynthesis: mechanisms of regulation, function and disease

The tricarboxylic acid cycle, nutrient oxidation, histone acetylation and synthesis of lipids, glycans and haem all require the cofactor coenzyme A (CoA). Although the sources and regulation of the acyl groups carried by CoA for these processes are heavily studied, a key underlying question is less often considered: how is production of CoA itself controlled? Here, we discuss the many cellular roles of CoA and the regulatory mechanisms that govern its biosynthesis from cysteine, ATP and the essential nutrient pantothenate (vitamin B5), or from salvaged precursors in mammals. Metabolite feedback and signalling mechanisms involving acetyl-CoA, other acyl-CoAs, acyl-carnitines, MYC, p53, PPARα, PINK1 and insulin- and growth factor-stimulated PI3K-AKT signalling regulate the vitamin B5 transporter SLC5A6/SMVT and CoA biosynthesis enzymes PANK1, PANK2, PANK3, PANK4 and COASY. We also discuss methods for measuring CoA-related metabolites, compounds that target CoA biosynthesis and diseases caused by mutations in pathway enzymes including types of cataracts, cardiomyopathy and neurodegeneration (PKAN and COPAN).

Potential key genes are expected to become biomarker for early diagnosis of colorectal cancer through bioinformatics analysis

Colorectal cancer (CRC) is the leading cause of cancer-related deaths in the world. The aim of this study was to identify the potential key genes, and associated pathways for early-onset CRC through bioinformatics methods. We integrated the gene expression patterns of CRC from three RNAseq datasets (GSE8671, GSE20916, GSE39582) from GEO database to identify DEGs between CRC and normal samples. We established a gene co-expression network through WGCNA. Through the WGCNA calculation, the genes were divided into six modules. The WGCNA analysis screened 242 genes associated with pathological stage and colorectal adenocarcinoma, 31 of which had the ability to predict OS with an AUC >0.7. The GSE39582 dataset identified 2040 DEGs between the CRC and normal samples. The two were intersected to obtain two genes: NPM1 and PANK3. The two genes were used as a threshold to divide the samples into high group and low group for survival analysis. Survival analysis showed that increased expression of both genes was significantly associated with a poorer prognosis. These two genes (NPM1 and PANK3) could be possible marker genes for early diagnosis of CRC, providing ideas for other experimental studies in the future.

Kinome-Wide Synthetic Lethal Screen Identifies PANK4 as a Modulator of Temozolomide Resistance in Glioblastoma

Temozolomide (TMZ) represents the cornerstone of therapy for glioblastoma (GBM). However, acquisition of resistance limits its therapeutic potential. The human kinome is an undisputable source of druggable targets, still, current knowledge remains confined to a limited fraction of it, with a multitude of under-investigated proteins yet to be characterized. Here, following a kinome-wide RNAi screen, pantothenate kinase 4 (PANK4) isuncovered as a modulator of TMZ resistance in GBM. Validation of PANK4 across various TMZ-resistant GBM cell models, patient-derived GBM cell lines, tissue samples, as well as in vivo studies, corroborates the potential translational significance of these findings. Moreover, PANK4 expression is induced during TMZ treatment, and its expression is associated with a worse clinical outcome. Furthermore, a Tandem Mass Tag (TMT)-based quantitative proteomic approach, reveals that PANK4 abrogation leads to a significant downregulation of a host of proteins with central roles in cellular detoxification and cellular response to oxidative stress. More specifically, as cells undergo genotoxic stress during TMZ exposure, PANK4 depletion represents a crucial event that can lead to accumulation of intracellular reactive oxygen species (ROS) and subsequent cell death. Collectively, a previously unreported role for PANK4 in mediating therapeutic resistance to TMZ in GBM is unveiled.

Acetyl-CoA biosynthesis drives resistance to histone acetyltransferase inhibition

Histone acetyltransferases (HATs) are implicated as both oncogene and nononcogene dependencies in diverse human cancers. Acetyl-CoA-competitive HAT inhibitors have emerged as potential cancer therapeutics and the first clinical trial for this class of drugs is ongoing (NCT04606446). Despite these developments, the potential mechanisms of therapeutic response and evolved drug resistance remain poorly understood. Having discovered that multiple regulators of de novo coenzyme A (CoA) biosynthesis can modulate sensitivity to CBP/p300 HAT inhibition (PANK3, PANK4 and SLC5A6), we determined that elevated acetyl-CoA concentrations can outcompete drug-target engagement to elicit acquired drug resistance. This not only affects structurally diverse CBP/p300 HAT inhibitors, but also agents related to an investigational KAT6A/B HAT inhibitor that is currently in Phase 1 clinical trials. Altogether, this work uncovers CoA metabolism as an unexpected liability of anticancer HAT inhibitors and will therefore buoy future efforts to optimize the efficacy of this new form of targeted therapy.

Pantothenate Kinase 4 Governs Lens Epithelial Fibrosis by Negatively Regulating Pyruvate Kinase M2-Related Glycolysis

Lens fibrosis is one of the leading causes of cataract in the elderly population. The primary energy substrate of the lens is glucose from the aqueous humor, and the transparency of mature lens epithelial cells (LECs) is dependent on glycolysis for ATP. Therefore, the deconstruction of reprogramming of glycolytic metabolism can contribute to further understanding of LEC epithelial-mesenchymal transition (EMT). In the present study, we found a novel pantothenate kinase 4 (PANK4)-related glycolytic mechanism that regulates LEC EMT. The PANK4 level was correlated with aging in cataract patients and mice. Loss of function of PANK4 significantly contributed to alleviating LEC EMT by upregulating pyruvate kinase M2 isozyme (PKM2), which was phosphorylated at Y105, thus switching oxidative phosphorylation to glycolysis. However, PKM2 regulation did not affect PANK4, demonstrating the downstream role of PKM2. Inhibition of PKM2 in Pank4-/- mice caused lens fibrosis, which supports the finding that the PANK4-PKM2 axis is required for LEC EMT. Glycolytic metabolism-governed hypoxia inducible factor (HIF) signaling is involved in PANK4-PKM2-related downstream signaling. However, HIF-1α elevation was independent of PKM2 (S37) but PKM2 (Y105) when PANK4 was deleted, which demonstrated that PKM2 and HIF-1α were not involved in a classic positive feedback loop. Collectively, these results indicate a PANK4-related glycolysis switch that may contribute to HIF-1 stabilization and PKM2 phosphorylation at Y105 and inhibit LEC EMT. The mechanism elucidation in our study may also shed light on fibrosis treatments for other organs.

Patient-Derived Cellular Models for Polytarget Precision Medicine in Pantothenate Kinase-Associated Neurodegeneration

The term neurodegeneration with brain iron accumulation (NBIA) brings together a broad set of progressive and disabling neurological genetic disorders in which iron is deposited preferentially in certain areas of the brain. Among NBIA disorders, the most frequent subtype is pantothenate kinase-associated neurodegeneration (PKAN) caused by pathologic variants in the PANK2 gene codifying the enzyme pantothenate kinase 2 (PANK2). To date, there are no effective treatments to stop the progression of these diseases. This review discusses the utility of patient-derived cell models as a valuable tool for the identification of pharmacological or natural compounds for implementing polytarget precision medicine in PKAN. Recently, several studies have described that PKAN patient-derived fibroblasts present the main pathological features associated with the disease including intracellular iron overload. Interestingly, treatment of mutant cell cultures with various supplements such as pantothenate, pantethine, vitamin E, omega 3, α-lipoic acid L-carnitine or thiamine, improved all pathophysiological alterations in PKAN fibroblasts with residual expression of the PANK2 enzyme. The information provided by pharmacological screenings in patient-derived cellular models can help optimize therapeutic strategies in individual PKAN patients.

Diagnosis and Treatment of Pantothenate Kinase-Associated Neurodegeneration (PKAN): A Systematic Review

A specific type of neurodegeneration with brain iron accumulation (NBIA) falls under the omit phenotypic continuum-early childhood development of progressive pantothenate kinase-associated neurodegeneration (PKAN). Classic PKAN is distinguished from atypical PKAN by stiffness, dystonia, dysarthria, and choreoathetosis. Pigmentary retinal degeneration is a widespread cause of classic PKAN. Atypical PKAN is distinguished by a later onset (>10 years), noticeable speech abnormalities, psychological disorders, and slower disease development. Studies designed to support various PKAN therapeutic strategies have highlighted the intricacy of coenzyme A (CoA) metabolism and the limitations of our present understanding of disease causation. Therefore, improvements in our knowledge of the causes and therapy of PKAN may have ramifications for our comprehension of other, more prevalent diseases. They may also shed fresh light on the physiological significance of CoA, a cofactor essential for the operation of several cellular metabolic processes. The existence of low but considerable PANK2 expression, which can be elevated in some mutations, provides necessary information that can justify using a hefty dose of pantothenate as a treatment. A more effective therapeutic approach can be achieved by comparing the effects of various currently available pharmacological alternatives on the pathophysiological alterations in fibroblasts and neuronal cells obtained from PKAN patients. The objective of this study is to educate and inform people about PKAN disease conditions such as treatment, diagnosis, and complications. These cell models will also help evaluate the effectiveness of future medicinal innovations. This review discusses the neurodegeneration generated by pantothenate kinase in cellular models, iron/lipofuscin in pantothenate kinase-related neurodegeneration, and treatment and diagnosis of PKAN.

Inherited Disorders of Coenzyme A Biosynthesis: Models, Mechanisms, and Treatments

Coenzyme A (CoA) is a vital and ubiquitous cofactor required in a vast number of enzymatic reactions and cellular processes. To date, four rare human inborn errors of CoA biosynthesis have been described. These disorders have distinct symptoms, although all stem from variants in genes that encode enzymes involved in the same metabolic process. The first and last enzymes catalyzing the CoA biosynthetic pathway are associated with two neurological conditions, namely pantothenate kinase-associated neurodegeneration (PKAN) and COASY protein-associated neurodegeneration (CoPAN), which belong to the heterogeneous group of neurodegenerations with brain iron accumulation (NBIA), while the second and third enzymes are linked to a rapidly fatal dilated cardiomyopathy. There is still limited information about the pathogenesis of these diseases, and the knowledge gaps need to be resolved in order to develop potential therapeutic approaches. This review aims to provide a summary of CoA metabolism and functions, and a comprehensive overview of what is currently known about disorders associated with its biosynthesis, including available preclinical models, proposed pathomechanisms, and potential therapeutic approaches.

Evidence for a Conserved Function of Eukaryotic Pantothenate Kinases in the Regulation of Mitochondrial Homeostasis and Oxidative Stress

Human PANK1, PANK2, and PANK3 genes encode several pantothenate kinase isoforms that catalyze the phosphorylation of vitamin B5 (pantothenic acid) to phosphopantothenate, a critical step in the biosynthesis of the major cellular cofactor, Coenzyme A (CoA). Mutations in the PANK2 gene, which encodes the mitochondrial pantothenate kinase (PanK) isoform, have been linked to pantothenate-kinase associated neurodegeneration (PKAN), a debilitating and often fatal progressive neurodegeneration of children and young adults. While the biochemical properties of these enzymes have been well-characterized in vitro, their expression in a model organism such as yeast in order to probe their function under cellular conditions have never been achieved. Here we used three yeast mutants carrying missense mutations in the yeast PanK gene, CAB1, which are associated with defective growth at high temperature and iron, mitochondrial dysfunction, increased iron content, and oxidative stress, to assess the cellular function of human PANK genes and functional conservation of the CoA-controlled processes between humans and yeast. Overexpression of human PANK1 and PANK3 in these mutants restored normal cellular activity whereas complementation with PANK2 was partial and could only be achieved with an isoform, PanK2^mtmΔ, lacking the mitochondrial transit peptide. These data, which demonstrate functional conservation of PanK activity between humans and yeast, set the stage for the use of yeast as a model system to investigate the impact of PKAN-associated mutations on the metabolic pathways altered in this disease.

Generation and Validation of an Anti-Human PANK3 Mouse Monoclonal Antibody

Coenzyme A (CoA) is an essential co-factor at the intersection of diverse metabolic pathways. Cellular CoA biosynthesis is regulated at the first committed step—phosphorylation of pantothenic acid—catalyzed by pantothenate kinases (PANK1,2,3 in humans, PANK3 being the most highly expressed). Despite the critical importance of CoA in metabolism, the differential roles of PANK isoforms remain poorly understood. Our investigations of PANK proteins as potential precision oncology collateral lethality targets (PANK1 is co-deleted as part of the PTEN locus in some highly aggressive cancers) were severely hindered by a dearth of commercial antibodies that can reliably detect endogenous PANK3 protein. While we successfully validated commercial antibodies for PANK1 and PANK2 using CRISPR knockout cell lines, we found no commercial antibody that could detect endogenous PANK3. We therefore set out to generate a mouse monoclonal antibody against human PANK3 protein. We demonstrate that a clone (Clone MDA-299-62A) can reliably detect endogenous PANK3 protein in cancer cell lines, with band-specificity confirmed by CRISPR PANK3 knockout and knockdown cell lines. Sub-cellular fractionation shows that PANK3 is overwhelmingly cytosolic and expressed broadly across cancer cell lines. PANK3 monoclonal antibody MDA-299-62A should prove a valuable tool for researchers investigating this understudied family of metabolic enzymes in health and disease.

Never-homozygous genetic variants in healthy populations are potential recessive disease candidates

The rapid pace with which genetic variants are now being determined means there is a pressing need to understand how they affect biological systems. Variants from healthy individuals have previously been used to study blood groups or HLA diversity and to identify genes that can apparently be nonfunctional in healthy people. These studies and others have observed a lower than expected frequency of homozygous individuals for potentially deleterious alleles, which would suggest that several of these alleles can lead to recessive disorders. Here we exploited this principle to hunt for potential disease variants in genomes from healthy people. We identified at least 108 exclusively heterozygous variants with evidence for an impact on biological function. We discuss several examples of candidate variants/genes including CCDC8, PANK3, RHD and NLRP12. Overall, the results suggest there are many, comparatively frequent, potentially lethal or disease-causing variants lurking in healthy human populations.

PI3K drives the de novo synthesis of coenzyme A from vitamin B5

In response to hormones and growth factors, the class I phosphoinositide-3-kinase (PI3K) signalling network functions as a major regulator of metabolism and growth, governing cellular nutrient uptake, energy generation, reducing cofactor production and macromolecule biosynthesis¹. Many of the driver mutations in cancer with the highest recurrence, including in receptor tyrosine kinases, Ras, PTEN and PI3K, pathologically activate PI3K signalling^2,3. However, our understanding of the core metabolic program controlled by PI3K is almost certainly incomplete. Here, using mass-spectrometry-based metabolomics and isotope tracing, we show that PI3K signalling stimulates the de novo synthesis of one of the most pivotal metabolic cofactors: coenzyme A (CoA). CoA is the major carrier of activated acyl groups in cells^4,5 and is synthesized from cysteine, ATP and the essential nutrient vitamin B5 (also known as pantothenate)^6,7. We identify pantothenate kinase 2 (PANK2) and PANK4 as substrates of the PI3K effector kinase AKT⁸. Although PANK2 is known to catalyse the rate-determining first step of CoA synthesis, we find that the minimally characterized but highly conserved PANK4⁹ is a rate-limiting suppressor of CoA synthesis through its metabolite phosphatase activity. Phosphorylation of PANK4 by AKT relieves this suppression. Ultimately, the PI3K–PANK4 axis regulates the abundance of acetyl-CoA and other acyl-CoAs, CoA-dependent processes such as lipid metabolism and proliferation. We propose that these regulatory mechanisms coordinate cellular CoA supplies with the demands of hormone/growth-factor-driven or oncogene-driven metabolism and growth.

The PI3K–PANK4 axis regulates coenzyme A synthesis, the abundance of acetyl-CoA, and CoA-dependent processes such as lipid metabolism, and these regulatory mechanisms coordinate cellular CoA supplies with the demands of hormone and growth-factor-driven or oncogene-driven metabolism and growth.

PKAN hiPS-Derived Astrocytes Show Impairment of Endosomal Trafficking: A Potential Mechanism Underlying Iron Accumulation

PKAN disease is caused by mutations in the PANK2 gene, encoding the mitochondrial enzyme pantothenate kinase 2, catalyzing the first and key reaction in Coenzyme A (CoA) biosynthetic process. This disorder is characterized by progressive neurodegeneration and excessive iron deposition in the brain. The pathogenic mechanisms of PKAN are still unclear, and the available therapies are only symptomatic. Although iron accumulation is a hallmark of PKAN, its relationship with CoA dysfunction is not clear. We have previously developed hiPS-derived astrocytes from PKAN patients showing iron overload, thus recapitulating the human phenotype. In this work, we demonstrated that PKAN astrocytes presented an increase in transferrin uptake, a key route for cellular iron intake via transferrin receptor-mediated endocytosis of transferrin-bound iron. Investigation of constitutive exo-endocytosis and vesicular dynamics, exploiting the activity-enriching biosensor SynaptoZip, led to the finding of a general impairment in the constitutive endosomal trafficking in PKAN astrocytes. CoA and 4-phenylbutyric acid treatments were found to be effective in partially rescuing the aberrant vesicular behavior and iron intake. Our results demonstrate that the impairment of CoA biosynthesis could interfere with pivotal intracellular mechanisms involved in membrane fusions and vesicular trafficking, leading to an aberrant transferrin receptor-mediated iron uptake.

Redesigning therapies for pantothenate kinase-associated neurodegeneration

Pantothenate Kinase-Associated Neurodegeneration (PKAN) is an incurable rare genetic disorder of children and young adults caused by mutations in the PANK2 gene, which encodes an enzyme critical for the biosynthesis of Coenzyme A. Although PKAN affects only a small number of patients, it shares several hallmarks of more common neurodegenerative diseases of older adults such as Alzheimer's and Parkinson's. Advances in etiological understanding and treatment of PKAN could therefore have implications for our understanding of more common diseases and may shed new lights on the physiological importance of Coenzyme A, a cofactor critical for the operation of various cellular metabolic processes. The large body of knowledge which accumulated over the years around PKAN pathology, including but not limited to studies of various PKAN models and therapies, has contributed not only to progress in our understanding of the disease, but as importantly, to the crystallization of key questions that guide future investigations of the disease. In this Review, we will summarize this knowledge and demonstrate how it forms the backdrop to new avenues of research.

Pantothenate and CoA biosynthesis in Apicomplexa and their promise as antiparasitic drug targets

The Apicomplexa phylum comprises thousands of distinct intracellular parasite species, including coccidians, haemosporidians, piroplasms, and cryptosporidia. These parasites are characterized by complex and divergent life cycles occupying a variety of host niches. Consequently, they exhibit distinct adaptations to the differences in nutritional availabilities, either relying on biosynthetic pathways or by salvaging metabolites from their host. Pantothenate (Pan, vitamin B5) is the precursor for the synthesis of an essential cofactor, coenzyme A (CoA), but among the apicomplexans, only the coccidian subgroup has the ability to synthesize Pan. While the pathway to synthesize CoA from Pan is largely conserved across all branches of life, there are differences in the redundancy of enzymes and possible alternative pathways to generate CoA from Pan. Impeding the scavenge of Pan and synthesis of Pan and CoA have been long recognized as potential targets for antimicrobial drug development, but in order to fully exploit these critical pathways, it is important to understand such differences. Recently, a potent class of pantothenamides (PanAms), Pan analogs, which target CoA-utilizing enzymes, has entered antimalarial preclinical development. The potential of PanAms to target multiple downstream pathways make them a promising compound class as broad antiparasitic drugs against other apicomplexans. In this review, we summarize the recent advances in understanding the Pan and CoA biosynthesis pathways, and the suitability of these pathways as drug targets in Apicomplexa, with a particular focus on the cyst-forming coccidian, Toxoplasma gondii, and the haemosporidian, Plasmodium falciparum.

A novel heteromeric pantothenate kinase complex in apicomplexan parasites

Coenzyme A is synthesised from pantothenate via five enzyme-mediated steps. The first step is catalysed by pantothenate kinase (PanK). All PanKs characterised to date form homodimers. Many organisms express multiple PanKs. In some cases, these PanKs are not functionally redundant, and some appear to be non-functional. Here, we investigate the PanKs in two pathogenic apicomplexan parasites, Plasmodium falciparum and Toxoplasma gondii. Each of these organisms express two PanK homologues (PanK1 and PanK2). We demonstrate that PfPanK1 and PfPanK2 associate, forming a single, functional PanK complex that includes the multi-functional protein, Pf14-3-3I. Similarly, we demonstrate that TgPanK1 and TgPanK2 form a single complex that possesses PanK activity. Both TgPanK1 and TgPanK2 are essential for T. gondii proliferation, specifically due to their PanK activity. Our study constitutes the first examples of heteromeric PanK complexes in nature and provides an explanation for the presence of multiple PanKs within certain organisms.

Non-targeted metabonomics to investigate the differences in the properties of ginseng and American ginseng based on rapid resolution liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry

The basic properties of herbal medicines are cold, hot, warm, and cool. The differentiation of these properties is important for the diagnosis and treatment of diseases. Ginseng and American ginseng possess opposite properties of warm and cool, respectively. At present, the mechanisms and the influence of steaming leading to the differences in their properties are not clear and require further investigation. Therefore, nontargeted metabonomics based on liquid chromatography-mass spectrometry was applied to investigate the effects of ginseng, American ginseng, and their variants on the changes in endogenous metabolites in rat urine. A total of 19 potential biomarkers were screened out and identified, of which 17, 7, and 5, were respectively related to warm, cool, and both warm and cool properties with opposite effects. The metabolic pathways corresponded to fatty acids, lipids, glycolysis, and energy metabolisms. The warm and tonic effects of red ginseng are stronger than those of ginseng and consistent with the theory of traditional Chinese medicine. The red American ginseng has cool property; however, the degree of coolness is less than that of American ginseng. This study provides a reference methodology to understand the effects of processing and mechanisms associated with the differences in the properties of herbal medicines.

Activation of Anopheles stephensi Pantothenate Kinase and Coenzyme A Biosynthesis Reduces Infection with Diverse Plasmodium Species in the Mosquito Host

Malaria parasites require pantothenate from both human and mosquito hosts to synthesize coenzyme A (CoA). Specifically, mosquito-stage parasites cannot synthesize pantothenate de novo or take up preformed CoA from the mosquito host, making it essential for the parasite to obtain pantothenate from mosquito stores. This makes pantothenate utilization an attractive target for controlling sexual stage malaria parasites in the mosquito. CoA is synthesized from pantothenate in a multi-step pathway initiated by the enzyme pantothenate kinase (PanK). In this work, we manipulated A. stephensi PanK activity and assessed the impact of mosquito PanK activity on the development of two malaria parasite species with distinct genetics and life cycles: the human parasite Plasmodium falciparum and the mouse parasite Plasmodium yoelii yoelii 17XNL. We identified two putative A. stephensi PanK isoforms encoded by a single gene and expressed in the mosquito midgut. Using both RNAi and small molecules with reported activity against human PanK, we confirmed that A. stephensi PanK manipulation was associated with corresponding changes in midgut CoA levels. Based on these findings, we used two small molecule modulators of human PanK activity (PZ-2891, compound 7) at reported and ten-fold EC50 doses to examine the effects of manipulating A. stephensi PanK on malaria parasite infection success. Our data showed that oral provisioning of 1.3 nM and 13 nM PZ-2891 increased midgut CoA levels and significantly decreased infection success for both Plasmodium species. In contrast, oral provisioning of 62 nM and 620 nM compound 7 decreased CoA levels and significantly increased infection success for both Plasmodium species. This work establishes the A. stephensi CoA biosynthesis pathway as a potential target for broadly blocking malaria parasite development in anopheline hosts. We envision this strategy, with small molecule PanK modulators delivered to mosquitoes via attractive bait stations, working in concert with deployment of parasite-directed novel pantothenamide drugs to block parasite infection in the human host. In mosquitoes, depletion of pantothenate through manipulation to increase CoA biosynthesis is expected to negatively impact Plasmodium survival by starving the parasite of this essential nutrient. This has the potential to kill both wild type parasites and pantothenamide-resistant parasites that could develop under pantothenamide drug pressure if these compounds are used as future therapeutics for human malaria.

Exploring Yeast as a Study Model of Pantothenate Kinase-Associated Neurodegeneration and for the Identification of Therapeutic Compounds

Mutations in the pantothenate kinase 2 gene (PANK2) are the cause of pantothenate kinase-associated neurodegeneration (PKAN), the most common form of neurodegeneration with brain iron accumulation. Although different disease models have been created to investigate the pathogenic mechanism of PKAN, the cascade of molecular events resulting from CoA synthesis impairment is not completely understood. Moreover, for PKAN disease, only symptomatic treatments are available. Despite the lack of a neural system, Saccharomyces cerevisiae has been successfully used to decipher molecular mechanisms of many human disorders including neurodegenerative diseases as well as iron-related disorders. To gain insights into the molecular basis of PKAN, a yeast model of this disease was developed: a yeast strain with the unique gene encoding pantothenate kinase CAB1 deleted, and expressing a pathological variant of this enzyme. A detailed functional characterization demonstrated that this model recapitulates the main phenotypes associated with human disease: mitochondrial dysfunction, altered lipid metabolism, iron overload, and oxidative damage suggesting that the yeast model could represent a tool to provide information on pathophysiology of PKAN. Taking advantage of the impaired oxidative growth of this mutant strain, a screening for molecules able to rescue this phenotype was performed. Two molecules in particular were able to restore the multiple defects associated with PKAN deficiency and the rescue was not allele-specific. Furthermore, the construction and characterization of a set of mutant alleles, allowing a quick evaluation of the biochemical consequences of pantothenate kinase (PANK) protein variants could be a tool to predict genotype/phenotype correlation.

Starvation causes female-to-male sex reversal through lipid metabolism in the teleost fish, medaka (Olyzias latipes)

The teleost fish, medaka (Oryzias latipes), employs the XX/XY genetic sex determination system. We show here that the phenotypic sex of medaka is affected by changes in lipid metabolism. Medaka larvae subjected to 5 days of starvation underwent female-to-male sex reversal. Metabolomic and RT-qPCR analyses indicated that pantothenate metabolism was suppressed by starvation. Consistently, inhibiting the pantothenate metabolic pathway caused sex reversal. The final metabolite in this pathway is coenzyme A, an essential factor for lipogenesis. Inhibiting fatty acid synthesis, the first step of lipogenesis, also caused sex reversal. The expression of dmrt1, a critical gene for male development, was suppressed by starvation, and a dmrt1 (Δ13) mutant did not show sex reversal under starvation. Collectively, these results indicate that fatty acid synthesis is involved in female-to-male sex reversal through ectopic expression of male gene dmrt1 under starvation.

Summary: We investigated the effects of starvation on sex differentiation in medaka. Starvation caused female-to-male sex reversal through pantothenate metabolism, fatty acid synthesis and dmrt1 expression.

Regulation of coenzyme A levels by degradation: the 'Ins and Outs'

Coenzyme A (CoA) is the predominant acyl carrier in mammalian cells and a cofactor that plays a key role in energy and lipid metabolism. CoA and its thioesters (acyl-CoAs) regulate a multitude of metabolic processes at different levels: as substrates, allosteric modulators, and via post-translational modification of histones and other non-histone proteins. Evidence is emerging that synthesis and degradation of CoA are regulated in a manner that enables metabolic flexibility in different subcellular compartments. Degradation of CoA occurs through distinct intra- and extracellular pathways that rely on the activity of specific hydrolases. The pantetheinase enzymes specifically hydrolyze pantetheine to cysteamine and pantothenate, the last step in the extracellular degradation pathway for CoA. This reaction releases pantothenate in the bloodstream, making this CoA precursor available for cellular uptake and de novo CoA synthesis. Intracellular degradation of CoA depends on specific mitochondrial and peroxisomal Nudix hydrolases. These enzymes are also active against a subset of acyl-CoAs and play a key role in the regulation of subcellular (acyl-)CoA pools and CoA-dependent metabolic reactions. The evidence currently available indicates that the extracellular and intracellular (acyl-)CoA degradation pathways are regulated in a coordinated and opposite manner by the nutritional state and maximize the changes in the total intracellular CoA levels that support the metabolic switch between fed and fasted states in organs like the liver. The objective of this review is to update the contribution of these pathways to the regulation of metabolism, physiology and pathology and to highlight the many questions that remain open.

Coenzyme A and Its Thioester Pools in Obese Zucker and Zucker Diabetic Fatty Rats

Feeding behavior is closely related to hypothalamic malonyl-CoA level in the brain and diet-induced obesity affects total CoA pools in liver. Herein, we performed a comprehensive analysis of the CoA pools formed in thirteen tissues of Zucker and Zucker diabetic fatty (ZDF) rats. Hypothalamic malonyl-CoA levels in obese rats remained low and were almost the same as those of lean rats, despite obese rats having much higher content of leptin, insulin, and glucose in their sera. Regardless of the fa-genotypes, larger total CoA pools were formed in the livers of ZDF rats and the size of hepatic total CoA pools in Zucker rats showed almost one tenth of the size of ZDF rats. The decreased total CoA pool sizes in Zucker rats was observed in the brown adipose tissues, while ZDF-fatty rats possessed 6% of total CoA pool in the lean rats in response to fa deficiency. This substantially lower CoA content in the obese rats would be disadvantageous to non-shivering thermogenesis. Thus, comparing the intracellular CoA behaviors between Zucker and ZDF rats, as well as the lean and fatty rats of each strain would help to elucidate features of obesity and type 2 diabetes in combination with result (s) of differential gene expression analysis and/or comparative genomics.

Emerging concepts in pseudoenzyme classification, evolution, and signaling

The 21st century is witnessing an explosive surge in our understanding of pseudoenzyme-driven regulatory mechanisms in biology. Pseudoenzymes are proteins that have sequence homology with enzyme families but that are proven or predicted to lack enzyme activity due to mutations in otherwise conserved catalytic amino acids. The best-studied pseudoenzymes are pseudokinases, although examples from other families are emerging at a rapid rate as experimental approaches catch up with an avalanche of freely available informatics data. Kingdom-wide analysis in prokaryotes, archaea and eukaryotes reveals that between 5 and 10% of proteins that make up enzyme families are pseudoenzymes, with notable expansions and contractions seemingly associated with specific signaling niches. Pseudoenzymes can allosterically activate canonical enzymes, act as scaffolds to control assembly of signaling complexes and their localization, serve as molecular switches, or regulate signaling networks through substrate or enzyme sequestration. Molecular analysis of pseudoenzymes is rapidly advancing knowledge of how they perform noncatalytic functions and is enabling the discovery of unexpected, and previously unappreciated, functions of their intensively studied enzyme counterparts. Notably, upon further examination, some pseudoenzymes have previously unknown enzymatic activities that could not have been predicted a priori. Pseudoenzymes can be targeted and manipulated by small molecules and therefore represent new therapeutic targets (or anti-targets, where intervention should be avoided) in various diseases. In this review, which brings together broad bioinformatics and cell signaling approaches in the field, we highlight a selection of findings relevant to a contemporary understanding of pseudoenzyme-based biology.