HIV-1 Nef-POTEE; A novel interaction modulates macrophage dissemination via mTORC2 signaling pathway.

AIMS: Human immunodeficiency virus -1 [HIV-1] Nef, localizes in different cellular compartments and modulates several cellular pathways. Nef promotes virus pathogenicity through alteration in cell surface receptor expression, apoptosis, protein trafficking etc. Nef regulates viral pathogenesis through interaction with different host proteins. Thus, molecular mechanisms of pathogenesis could be deciphered by identifying novel Nef interacting proteins. MAIN METHODS: HIV-1 Nef interacting proteins were identified by pull down assay and MALDI-TOF analysis. The interaction was further validated through mammalian two hybrid assay. Functional role of this interaction was identified by immunoprecipitation assay, cell invasion and cell migration studies. Fold Change in mRNA levels of CD163, CD206, CCL17 and CCL18 was analyzed using qPCR. KEY FINDINGS: In current study, C. elegans protein ACT4C and its human homolog POTEE was identified to be interacting with Nef. This interaction activates mTORC2 complex, which in-turn activates AKT and PKC-α. The activation of mTORC2 complex was found to be initiated by the interaction of Nef, mTORC2, Rictor to POTEE. The cellular phenotype and functions affected by Nef-POTEE interaction resulted in significant increase in cell invasion and migration of macrophages (MΦ). SIGNIFICANCE: MΦ is primary target of HIV-1 infection where HIV-1 replicates and polarizes immunosuppressive M2 phenotype. Combine effect of M2 phenotype and Viral-host protein interactions compromise the MΦ associated physiological functions. Infected MΦ dissemination into other system also leads to HIV-1 induced malignancies. Therefore, targeting POTEE-Nef interaction can lead to formulating better therapeutic strategy against HIV-1.

HIV-1 Nef binds with human GCC185 protein and regulates mannose 6 phosphate receptor recycling.

HIV-1 Nef modulates cellular function that enhances viral replication in vivo which culminate into AIDS pathogenesis. With no enzymatic activity, Nef regulates cellular function through host protein interaction. Interestingly, trans-cellular introduction of recombinant Nef protein in Caenorhabditis elegans results in AIDS like pathogenesis which might share common pathophysiology because the gene sequence of C. elegans and humans share considerable homology. Therefore employing C. elegans based initial screen complemented with sequence based homology search we identified GCC185 as novel host protein interacting with HIV-1 Nef. The detailed molecular characterization revealed N-terminal EEEE65 acidic domain of Nef as key region for interaction. GCC185 is a tethering protein that binds with Rab9 transport vesicles. Our results show that Nef-GCC185 interaction disrupts Rab9 interaction resulting in delocalization of CI-MPR (cation independent Mannose 6 phosphate receptor) resulting in elevated secretion of hexosaminidase. In agreement with this, our studies identified novel host GCC185 protein that interacts with Nef EEEE65 acidic domain interfering GCC185-Rab9 vesicle membrane fusion responsible for retrograde vesicular transport of CI-MPR from late endosomes to TGN. In light of existing report suggesting critical role of Nef-GCC185 interaction reveals valuable mechanistic insights affecting specific protein transport pathway in docking of late endosome derived Rab9 bearing transport vesicle at TGN elucidating role of Nef during viral pathogenesis.

Iridoid compound 10-O-trans-p-coumaroylcatalpol extends longevity and reduces α synuclein aggregation in Caenorhabditis elegans.

Aging, the major cause of several ailments has led to intense exploration of potential drugs that delay aging and its associated effects. We mined the information on traditional Indian medicines and identified an iridoid, 10-O-trans-p-Coumaroylcatalpol (OCC), a major ingredient of Premna integrifolia Linn. (syn: Premna serratifolia). OCC forms an important constituent of famous herbal formulation 'Dashmula', a ten herb formulation, commonly used for its various medicinal properties. Employing model system C. elegans, the effect of OCC on life span, stress resistance, chemotaxis, the content of reactive oxygen species (ROS) and on the aggregation of alpha synuclein was studied. OCC extended the mean life span of nematodes, increased their tolerance against chemical induced stress, improved the chemotaxis index and reduced the ROS content. Further, the aggregation of Parkinson's disease (PD) associated protein, alpha synuclein (asyn), was decreased when transgenic a-syn expressing worms were raised on OCC mixed diet. We extended the studies further to explore the possible genetic mechanism that mediates the observed effects of OCC. Employing the genetic knockout mutants TK22 [mev-1(kn1)III]; GR1307 [daf-16(mgDf50)I]; VC199 [sir-2.1(ok434)IV] and transgenic GFP expressing strain TJ356 [zls356; DAF-16::GFP], our studies revealed that the effects were mediated by daf-16 and not by sir-2.1 or mev-1. Our results indicate that OCC has the ability to ameliorate a-syn aggregation, reduce oxidative stress and promote longevity in C. elegans via activation of longevity promoting transcription factor DAF-16. Thus, OCC may serve as a lead compound of plant origin for important nutraceutical intervention against aging and age associated PD.

RNAi of cat-2, a putative tyrosine hydroxylase, increases alpha synuclein aggregation and associated effects in transgenic C. elegans.

Neurodegenerative Parkinson's disease (PD) is a multifactorial disorder; effects like alpha synuclein aggregation, low dopamine levels and dopaminergic neurodegeneration are considered to be hallmarks of the disease. Several recent studies have pointed towards an important role of enzyme tyrosine hydroxylase (TH) in the pathophysiology of PD. We embarked on the present studies to explore the mechanistic role of C. elegans gene cat-2, a putative tyrosine hydroxylase, in PD. Utilizing the powerful genetic model system C. elegans, which has previously provided critical understanding of several human diseases, we employed a reverse genetics approach via RNAi mediated gene silencing of cat-2, to study various disease related effects in three different transgenic strains of the nematode. Knocking-down of cat-2 led to increase in aggregation of alpha synuclein, as was studied via expression of YFP. Similarly the silencing of cat-2 had significant effects on associated endpoints including oxidative stress, lipid content and neurotransmission; exemplifying the role of cat-2, the putative tyrosine hydroxylase, in Parkinsonism of the nematode model. The findings are significant as this model could further be used to study the entire associated pathway in greater detail and with the advantages that the model system C. elegans presents, the knockdown of cat-2 in the alpha synuclein expressing strain, could be employed for screening potential pharmacological agents targeted at TH which could lead to designing of possible therapeutic interventions for the disease.

Anti-Parkinsonian effects of Bacopa monnieri: insights from transgenic and pharmacological Caenorhabditis elegans models of Parkinson's disease.

Neurodegenerative Parkinson's disease (PD) is associated with aggregation of protein alpha synuclein and selective death of dopaminergic neurons, thereby leading to cognitive and motor impairment in patients. The disease has no complete cure yet; the current therapeutic strategies involve prescription of dopamine agonist drugs which turn ineffective after prolonged use. The present study utilized the powerful genetics of model system Caenorhabditis elegans towards exploring the anti-Parkinsonian effects of a neuro-protective botanical Bacopa monnieri. Two different strains of C. elegans; a transgenic model expressing "human" alpha synuclein [NL5901 (P(unc-54)::alphasynuclein::YFP+unc-119)], and a pharmacological model expressing green fluorescent protein (GFP) specifically in the dopaminergic neurons [BZ555 (P(dat-1)::GFP)] treated with selective catecholaminergic neurotoxin 6-hydroxy dopamine (6-OHDA), were employed for the study. B. monnieri was chosen for its known neuroprotective and cognition enhancing effects. The study examined the effect of the botanical, on aggregation of alpha synuclein, degeneration of dopaminergic neurons, content of lipids and longevity of the nematodes. Our studies show that B. monnieri reduces alpha synuclein aggregation, prevents dopaminergic neurodegeneration and restores the lipid content in nematodes, thereby proving its potential as a possible anti-Parkinsonian agent. These findings encourage further investigations on the botanical, and its active constituent compounds, as possible therapeutic intervention against Parkinson's disease.

Sir-2.1 modulates 'calorie-restriction-mediated' prevention of neurodegeneration in Caenorhabditis elegans: implications for Parkinson's disease.

The phenomenon of aging is known to modulate many disease conditions including neurodegenerative ailments like Parkinson's disease (PD) which is characterized by selective loss of dopaminergic neurons. Recent studies have reported on such effects, as calorie restriction, in modulating aging in living systems. We reason that PD, being an age-associated neurodegenerative disease might be modulated by interventions like calorie restriction. In the present study we employed the transgenic Caenorhabditis elegans model (P(dat-1)::GFP) expressing green fluorescence protein (GFP) specifically in eight dopaminergic (DA) neurons. Selective degeneration of dopaminergic neurons was induced by treatment of worms with 6-hydroxy dopamine (6-OHDA), a selective catecholaminergic neurotoxin, followed by studies on effect of calorie restriction on the neurodegeneration. Employing confocal microscopy of the dopaminergic neurons and HPLC analysis of dopamine levels in the nematodes, we found that calorie restriction has a preventive effect on dopaminergic neurodegeneration in the worm model. We further studied the role of sirtuin, sir-2.1, in modulating such an effect. Studies employing RNAi induced gene silencing of nematode sir-2.1, revealed that presence of Sir-2.1 is necessary for achieving the protective effect of calorie restriction on dopaminergic neurodegeneration. Our studies provide evidence that calorie restriction affords, an sir-2.1 mediated, protection against the dopaminergic neurodegeneration, that might have implications for neurodegenerative Parkinson's disease.