Han S et al. (2015) Science "Cell biology. Lysosomal lipid lengthens life span."

Han S, Brunet A

[Science, 2015]

Han S et al. (2023) Genes (Basel) "A Chemoptogenetic Tool for Spatiotemporal Induction of Oxidative DNA Lesions In Vivo."

Aceto A, Bruchez MP, Sims A, Gurkar AU, Schmidt BF, Han S

[Genes (Basel), 2023]

Oxidative nuclear DNA damage increases in all tissues with age in multiple animal models, as well as in humans. However, the increase in DNA oxidation varies from tissue to tissue, suggesting that certain cells/tissues may be more vulnerable to DNA damage than others. The lack of a tool that can control dosage and spatiotemporal induction of oxidative DNA damage, which accumulates with age, has severely limited our ability to understand how DNA damage drives aging and age-related diseases. To overcome this, here we developed a chemoptogenetic tool that produces 8-oxoguanine (8-oxoG) at DNA in a whole organism, Caenorhabditis elegans. This tool uses di-iodinated malachite green (MG-2I) photosensitizer dye that generates singlet oxygen, 1O2, upon fluorogen activating peptide (FAP) binding and excitation with far-red light. Using our chemoptogenetic tool, we are able to control generation of singlet oxygen ubiquitously or in a tissue-specific manner, including in neurons and muscle cells. To induce oxidative DNA damage, we targeted our chemoptogenetic tool to histone, his-72, that is expressed in all cell types. Our results show that a single exposure to dye and light is able to induce DNA damage, promote embryonic lethality, lead to developmental delay, and significantly reduce lifespan. Our chemoptogenetic tool will now allow us to assess the cell autonomous versus non-cell autonomous role of DNA damage in aging, at an organismal level.

Han S et al. (2017) Nature "Mono-unsaturated fatty acids link H3K4me3 modifiers to C. elegans lifespan."

Mair WB, Hebestreit K, Brunet A, Silva-Garcia CG, Schroeder EA, Han S

[Nature, 2017]

Chromatin and metabolic states both influence lifespan, but how they interact in lifespan regulation is largely unknown. The COMPASS chromatin complex, which trimethylates lysine 4 on histone H3 (H3K4me3), regulates lifespan in Caenorhabditis elegans. However, the mechanism by which H3K4me3 modifiers affect longevity, and whether this mechanism involves metabolic changes, remain unclear. Here we show that a deficiency in H3K4me3 methyltransferase, which extends lifespan, promotes fat accumulation in worms with a specific enrichment of mono-unsaturated fatty acids (MUFAs). This fat metabolism switch in H3K4me3 methyltransferase-deficient worms is mediated at least in part by the downregulation of germline targets, including S6 kinase, and by the activation of an intestinal transcriptional network that upregulates delta-9 fatty acid desaturases. Notably, the accumulation of MUFAs is necessary for the lifespan extension of H3K4me3 methyltransferase-deficient worms, and dietary MUFAs are sufficient to extend lifespan. Given the conservation of lipid metabolism, dietary or endogenous MUFAs could extend lifespan and healthspan in other species, including mammals.

Han S et al. (2020) Biochem Biophys Res Commun "VPS-22/SNF8 regulates longevity via modulating the activity of DAF-16 in C.elegans."

Wang D, Yuan F, Wang J, Lv Y, Han S, Gao M

[Biochem Biophys Res Commun, 2020]

Aging is regulated by complex signaling networks, the details of which remain poorly understood. Here, we demonstrate that VPS-22/SNF8, a component of endosomal sorting complex required for transport-II (ESCRT-II), regulates the lifespan of C.elegans. In this study we show that worms with vps-22/snf8 gene knockdown had a shorter lifespan than wild-type worms. The expression pattern of VPS-22/SNF8 in C.elegans was highly similar to that of DAF-16. Knockout of daf-16 in C.elegans shortened the worms' lifespan; however, reducing the expression of vps-22/snf8 in daf-16 null worms did not further shorten their lifespan, indicating that vps-22/snf8 and daf-16 may act in the same signaling pathway to regulate longevity. Over-expression of daf-16 rescued the short-lived phenotype of vps-22/snf8 knockdown worms. Moreover, down-regulation of vps-22/snf8 decreased the nuclear localization of DAF-16 and modulated the expression of daf-16 downstream genes that regulate longevity in C.elegans. In summary, our results indicate that vps-22/snf8 can regulate the longevity of C.elegans by partially modulating the activity of daf-16. These findings may help us to better understand the mechanisms of aging.

Han S et al. (2012) J Biol Chem "Nuclear envelope phosphatase 1-regulatory subunit 1 (formerly TMEM188) is the metazoan Spo7p ortholog and functions in the lipin activation pathway."

Grishin N, Bahmanyar S, Reue K, Goodman JM, Dixon JE, Oegema K, Graham M, Han S, Zhang P, Crooke R

[J Biol Chem, 2012]

Lipin-1 catalyzes the formation of diacylglycerol from phosphatidic acid. Lipin-1 mutations cause lipodystrophy in mice and acute myopathy in humans. It is heavily phosphorylated, and the yeast ortholog Pah1p becomes membrane-associated and active upon dephosphorylation by the Nem1p-Spo7p membrane complex. A mammalian ortholog of Nem1p is the C-terminal domain nuclear envelope phosphatase 1 (CTDNEP1, formerly "dullard"), but its Spo7p-like partner is unknown, and the need for its existence is debated. Here, we identify the metazoan ortholog of Spo7p, TMEM188, renamed nuclear envelope phosphatase 1-regulatory subunit 1 (NEP1-R1). CTDNEP1 and NEP1-R1 together complement a nem1spo7 strain to block endoplasmic reticulum proliferation and restore triacylglycerol levels and lipid droplet number. The two human orthologs are in a complex in cells, and the amount of CTDNEP1 is increased in the presence of NEP1-R1. In the Caenorhabditis elegans embryo, expression of nematode CTDNEP1 and NEP1-R1, as well as lipin-1, is required for normal nuclear membrane breakdown after zygote formation. The expression pattern of NEP1-R1 and CTDNEP1 in human and mouse tissues closely mirrors that of lipin-1. CTDNEP1 can dephosphorylate lipins-1a, -1b, and -2 in human cells only in the presence of NEP1-R1. The nuclear fraction of lipin-1b is increased when CTDNEP1 and NEP1-R1 are co-expressed. Therefore, NEP1-R1 is functionally conserved from yeast to humans and functions in the lipin activation pathway.

Han, S. et al. (2011) International Worm Meeting "Growth cone guidance receptors modulate mitochondrial morphology and function via a secreted moiety of the VAPB/ALS8 protein, the major sperm protein domain."

Haueter, C., Han, S., Miller, M.A., Bellen, H.J., Tsuda, H., Cottee, P., Vibbert, J., Prasain, J., Yang, Y.

[International Worm Meeting, 2011]

Mitochondria are obligate endosymbionts that provide cells with energy and metabolic functions critical for their survival. Mitochondrial morphology and subcellular localization can be coordinated among different cells, but the mechanisms are not understood. Here we show that C. elegans, Drosophila, and human VAPB/ALS8 major sperm protein domains (MSPs), which are implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, comprise a hormone class that modulates mitochondrial position, morphology, division (fission), and function. MSPs transduce signals to mitochondria through Roundabout and Lar-like growth cone guidance receptors that remodel the actin cytoskeleton. We show that neurons secrete MSPs to control actin-related protein 2/3 complex activity in striated muscle, stabilizing mitochondria at actin- rich I-bands. Our results indicate that secreted MSPs promote energy production and metabolism by regulating mitochondrial localization and function. Hence, extracellular signals that influence the actin cytoskeleton may be important regulators of mitochondrial activity.

Hans S et al. (2019) J Glob Antimicrob Resist "Magnesium deprivation affects cellular circuitry involved in drug resistance and virulence in Candida albicans."

Hameed S, Fatima Z, Hans S

[J Glob Antimicrob Resist, 2019]

OBJECTIVES: Candida albicans has to struggle for the limited micronutrients present in the hostile niche. One such significant environmental factor that C. albicans must surmount is magnesium (Mg) limitation. Herein, we aimed to study the effect of Mg deprivation on drug resistance mechanisms and virulence traits of C. albicans. METHODS: Drug susceptibilities against C. albicans SC5314was measured by broth microdilution and spot assay. Drug efflux pump activity was measured by substrate R6G efflux. Membrane intactness was studied by propidium iodide influx and ergosterol levels by alcoholic KOH method. Metabolic flexibility was studied by enzymatic activities of glyoxylate cycle. Virulence factors were assessed by yeast to hyphae, biofilm formation and cell adherence. In-vivo study was performed by Caenorhabditis elegans infection model. RESULTS: We found that Mg chelation leads to potentiation of membrane targeting antifungals. We explored the role of Mg on membrane homeostasis and found significant differences in ergosterol levels. Interestingly we also explored that Mg deprivation impedes metabolic flexibility of C. albicans SC5314 by inhibiting glyoxylate cycle enzymes. Furthermore, Mg deprivation inhibited potential virulence traits including morphological transition, biofilm formation and buccal epithelial cell adherence. All the disrupted targets were validated by RT-PCR which corroborates our findings. Lastly, we demonstrated the enhanced survival of C. albicans SC5314 infected Caenorhabditis elegans model under Mg deprivation. CONCLUSION: In view of the restricted growth of C. albicans in Mg deficient environment, approaches could be utilized to boost the effectiveness of existing antifungals thereby improving the management of fungal infections.

Hans S et al. (2019) J Mycol Med "Retrograde signaling disruption influences ABC superfamily transporter, ergosterol and chitin levels along with biofilm formation in Candida albicans."

Hans S, Hameed S, Fatima Z

[J Mycol Med, 2019]

OBJECTIVE: The rise in fungal infections is alarming due to emergence of multidrug drug resistance (MDR). Hence elucidating novel drug targets to circumvent the problem of MDR warrants immediate attention. This study analyzes the effect of retrograde (RTG) signaling disruption on major MDR mechanisms and virulence of the human pathogenic fungal species Candida albicans. MATERIAL AND METHODS: Drug transporter activity was measured by rhodamine 6G (R6G) efflux. Membrane damage was studied by propidium iodide intake and ergosterol level determination. Cell wall effect was estimated by quantifying chitin levels and cell sedimentation rate. Biofilm formation was visualized by calcoflour white and crystal violet staining and measured by dry mass and MTT assay. Cell adherence to buccal epithelial cell was determined by trypan blue staining and MTT assay. Virulence was studied using nematode model Caenorhabditiselegans. RESULT: We demonstrated that mutant of transcription factor CaRTG3 leads to impaired efflux activity of ATP Binding Cassette (ABC) superfamily multidrug transporters. We further uncover that rtg3 mutant exhibited a disrupted membrane, decreased ergosterol levels and increased chitin content. Furthermore, RTG signaling disruption leads to inhibited biofilm formation and cell adherence to buccal epithelial cells. Lastly, rtg3 mutant displayed a reduced infectivity in C.elegans illustrating its vulnerability as antifungal target. Interestingly, all the abrogated phenotypes could be rescued in the revertant strain of rtg3 mutant. CONCLUSION: Present study establishes a link between RTG signaling, drug efflux and biofilm formation and validates CaRTG3 as antifungal target. Intricate studies are needed to further understand and exploit this therapeutic opportunity.

Hans S et al. (2020) Microb Pathog "Rec A disruption unveils cross talk between DNA repair and membrane damage, efflux pump activity, biofilm formation in Mycobacterium smegmatis."

Hameed S, Hans S, Purkait D, Bansal M, Fatima Z, Nandan S

[Microb Pathog, 2020]

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) has emerged in recent decades as one of the leading causes of mortality worldwide. The burden of TB is alarmingly high, with one third affected global population as reported by WHO. Short-course treatment with an antibiotic is a powerful weapon to treat infection of susceptible MTB strain, however; MTB has developed resistance to anti-TB drugs, which is an escalating global health crisis. Thus there is urgent need to identify new drug targets. RecA is a 38 kilodalton protein required for the repair and maintenance of DNA and regulation of the SOS response. The objective of this study is to understand the effect of disruption of RecA gene (deletion mutant disA from previous study) in a surrogate model for MTB, Mycobacterium smegmatis. This study demonstrated that disruption of RecA causes enhanced susceptibility towards rifampicin and generation of ROS leading to lipid peroxidation and impaired membrane homeostasis as depicted by altered cell membrane permeability and efflux pump activity. Mass spectrometry based lipidomic analysis revealed decreased mycolic acid moieties, phosphatidylinositol mannosides (PIM), Phthiocerol dimycocerosate (DIM). Furthermore, biofilm formation was considerably reduced. Additionally, we have validated all the disrupted phenotypes by RT-PCR which showed a good correlation with the biochemical assays. Lastly, RecA mutant displayed reduced infectivity in Caenorhabditis elegans illustrating its vulnerability as antimycobacterial target. Together, present study establishes a link between DNA repair, drug efflux and biofilm formation and validates RecA as an effective drug target. Intricate studies are needed to further understand and exploit this therapeutic opportunity.

Han H-P et al. (1992) Worm Breeder's Gazette "Expression and Localization of the cha-1 and unc-17 Gene Products"

Rand JB, Duerr JS, Han H-P

[Worm Breeder's Gazette, 1992]

EXPRESSION AND LOCALIZATION OF THE cha-l AND unc-17 GENE PRODUCTS He-ping Han, Janet Duerr, and Jim Rand, Oklahoma Medlcal Research Foundation, Oklahoma Clty, OK 73104