Biology subjects

Huynh, J.

Publications and source records attributed to Huynh, J..

3 recordsLinked to original sources

bioRxiv2022

Genetic inactivation of the USP19 deubiquitinase regulates a-synuclein ubiquitination and inhibits accumulation of Lewy body like aggregates in mice

The USP19 deubiquitinase is found in a locus associated with Parkinsons Disease (PD), interacts with heat shock proteins and promotes secretion of a-synuclein (a-syn) through the misfolding associated protein secretion (MAPS) pathway. Since these processes might modulate the processing of a-syn aggregates during the progression of PD, we tested the effect of USP19 knockout (KO) in mice expressing the A53T mutation of a-syn and in whom a-syn preformed fibrils (PFF) had been injected in the striatum. Compared to WT, KO brains showed decreased accumulation of phospho-synuclein (pSyn) positive aggregates. The improved pathology was associated with less activation of microglia, higher levels of synaptic marker proteins and improved performance in a tail suspension test. Exposure of primary neurons from WT and KO mice to PFF in vitro also led to decreased accumulation of pSyn aggregates. KO did not affect uptake of PFF in the cultured neurons. It also did not affect the propagation of aggregates as assessed by exposing WT or KO neurons to PFF and measuring pSyn positive aggregates in non-exposed adjacent neurons separated using a microfluidics device. We conclude that USP19 instead modulates intracellular dynamics of aggregates. Indeed, at the early time following PFF injection when the number of pSyn positive neurons were similar in WT and KO brains, the KO neurons contained less aggregates. KO brain aggregates stained more intensely with anti-ubiquitin antibodies. Immunoprecipitation of soluble proteins from primary neurons exposed to PFF with antibodies to ubiquitin or pSyn showed higher levels of ubiquitinated a-syn oligomeric species in the KO neurons. We propose that the improved pathology in USP19 KO brains may arise from decreased formation or enhanced clearance of the more ubiquitinated aggregates and/or enhanced disassembly towards more soluble oligomeric species. USP19 inhibition may represent a novel therapeutic approach that targets the intracellular dynamics of a-syn complexes.

neuroscience↗

bioRxiv2022

A phospho-switch provided by LRR receptor-like kinase, ALK1/QSK1/KIN7, prioritizes ABCG36/PEN3/PDR8 transport toward defense

Based on its proposed substrate preferences, the ABC transporter, ABCG36/PDR8/PEN3, from the model plant Arabidopsis stands at the cross-road between growth and defence. Recently, ABCG36 was shown to export a few indolic compounds, including the auxin precursor, indole-3-butyric acid (IBA), and to be implicated in the export of the major phytoalexin of Arabidopsis, camalexin, although clear-cut proof of camalexin transport activity is still lacking. Here we provide strong evidence that ABCG36 catalyses the direct, ATP-dependent export of camalexin over the plasma membrane, however, most likely in functional interplay with non-camalexin transporting ABCG isoforms. We identify the leucin-rich repeat receptor-like kinase, Auxin-induced LRR Kinase1 (ALK1/KIN7/QSK1), as a functional kinase to physically interact with and phosphorylate ABCG36. ABCG36 phosphorylation by ALK1 represses unilaterally IBA but not camalexin export leading to a prioritization of ABCG transport toward defense. As a consequence, phospho-dead mutants of ABCG36, like alk1 and abcg36 alleles, are hypersensitive toward infection with the root pathogen, F. oxysporum, caused by elevated fungal progression. Our findings indicate a novel, direct regulatory circuit between a receptor kinase and an ABC transporter determining transporter substrate specificity. It appears that growth and defense balance decisions in plants are performed on the transporter level by means of a reversible phospho-switch.

plant biology↗

bioRxiv2021

Protein interaction analysis of Plasmodium falciparum circumsporozoite protein variants with human immunoproteins explains RTS,S vaccine efficacy in Ghana

BackgroundThe worlds first malaria vaccine RTS,S provides only partial protection against Plasmodium falciparum infections. The explanation for such low efficacy is unclear. This study examined the associations of parasite genetic variations with binding affinity to human immunological proteins including human leukocyte antigen (HLA) and T cell receptors (TCR) involved in RTS,S-induced immune responses. MethodsMultiplicity of infections was determined by amplicon deep sequencing of merozoite surface protein 1 (PfMSP1). Genetic variations in the C-terminal of circumsporozoite protein (PfMSP1) gene were examined across 88 samples of P. falciparum collected from high and low transmission settings of Ghana. Binding interactions of PfMSP1 variants and HLA/TCR were analyzed using NetChop and HADDOCK predictions. Anti-CSP IgG levels were measured by ELISA in a subset of 10 samples. FindingsHigh polyclonality was detected among P. falciparum infections. A total 27 CSP haplotypes were detected among samples. A significant correlation was detected between the CSP and MSP multiplicity of infection (MOI). No clear clustering of haplotypes was observed by geographic regions. The number of genetic differences in PfCSP between 3D7 and non-3D7 variants does not influence binding interactions to HLA/T cells nor anti-CSP IgG levels. Nevertheless, PfCSP peptide length significantly affects its molecular weight and binding affinity to the HLA. InterpretationsThe presence of multiple non-3D7 strains among P. falciparum infections in Ghana impact the effectiveness of RTS,S. Longer PfCSP peptides may elicit a stronger immune response and should be considered in future version RTS,S. The molecular mechanisms of RTS,S cell-mediated immune responses related to longer CSP peptides warrants further investigations.

bioinformatics↗