Lactobacillus plantarum PS128 alleviates neurodegenerative progression in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse models of Parkinson's disease.

Evidence suggests that the Parkinson's disease (PD) pathogenesis is strongly associated with bidirectional pathways in the microbiota-gut-brain axis (MGBA), and psychobiotics may inhibit PD progression. We previously reported that the novel psychobiotic strain, Lactobacillus plantarum PS128 (PS128), ameliorated abnormal behaviors and modulated neurotransmissions in dopaminergic pathways in rodent models. Here, we report that orally administering PS128 for 4 weeks significantly alleviated the motor deficits, elevation in corticosterone, nigrostriatal dopaminergic neuronal death, and striatal dopamine reduction in 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced PD mouse models. PS128 ingestion suppressed glial cell hyperactivation and increased norepinephrine and neurotrophic factors in the striatum of the PD-model mice. PS128 administration also attenuated MPTP-induced oxidative stress and neuroinflammation in the nigrostriatal pathway. Fecal analysis showed that PS128 modulated the gut microbiota. L. plantarum abundance was significantly increased along with methionine biosynthesis-related microbial modules. PS128 also suppressed the increased family Enterobacteriaceae and lipopolysaccharide and peptidoglycan biosynthesis-related microbial modules caused by MPTP. In conclude, PS128 ingestion alleviated MPTP-induced motor deficits and neurotoxicity.PS128 supplementation inhibited neurodegenerative processes in PD-model mice and may help prevent PD.

Experimental evolution reveals a general role for the methyltransferase Hmt1 in noise buffering.

Cell-to-cell heterogeneity within an isogenic population has been observed in prokaryotic and eukaryotic cells. Such heterogeneity often manifests at the level of individual protein abundance and may have evolutionary benefits, especially for organisms in fluctuating environments. Although general features and the origins of cellular noise have been revealed, details of the molecular pathways underlying noise regulation remain elusive. Here, we used experimental evolution of Saccharomyces cerevisiae to select for mutations that increase reporter protein noise. By combining bulk segregant analysis and CRISPR/Cas9-based reconstitution, we identified the methyltransferase Hmt1 as a general regulator of noise buffering. Hmt1 methylation activity is critical for the evolved phenotype, and we also show that two of the Hmt1 methylation targets can suppress noise. Hmt1 functions as an environmental sensor to adjust noise levels in response to environmental cues. Moreover, Hmt1-mediated noise buffering is conserved in an evolutionarily distant yeast species, suggesting broad significance of noise regulation.

Arfaptin-1 negatively regulates Arl1-mediated retrograde transport.

The small GTPase Arf-like protein 1 (Arl1) is well known for its role in intracellular vesicular transport at the trans-Golgi network (TGN). In this study, we used differential affinity chromatography combined with mass spectrometry to identify Arf-interacting protein 1b (arfaptin-1b) as an Arl1-interacting protein and characterized a novel function for arfaptin-1 (including the arfaptin-1a and 1b isoforms) in Arl1-mediated retrograde transport. Using a Shiga-toxin subunit B (STxB) transportation assay, we demonstrated that knockdown of arfaptin-1 accelerated the retrograde transport of STxB from the endosome to the Golgi apparatus, whereas Arl1 knockdown inhibited STxB transport compared with control cells. Arfaptin-1 overexpression, but not an Arl1 binding-defective mutant (arfaptin-1b-F317A), consistently inhibited STxB transport. Exogenous arfaptin-1 expression did not interfere with the localization of the Arl1-interacting proteins golgin-97 and golgin-245 to the TGN and vice versa. Moreover, we found that the N-terminal region of arfaptin-1 was involved in the regulation of retrograde transport. Our results show that arfaptin-1 acts as a negative regulator in Arl1-mediated retrograde transport and suggest that different functional complexes containing Arl1 form in distinct microdomains and are responsible for different functions.

The Hsp90-dependent proteome is conserved and enriched for hub proteins with high levels of protein-protein connectivity.

Hsp90 is one of the most abundant and conserved proteins in the cell. Reduced levels or activity of Hsp90 causes defects in many cellular processes and also reveals genetic and nongenetic variation within a population. Despite information about Hsp90 protein-protein interactions, a global view of the Hsp90-regulated proteome in yeast is unavailable. To investigate the degree of dependency of individual yeast proteins on Hsp90, we used the "stable isotope labeling by amino acids in cell culture" method coupled with mass spectrometry to quantify around 4,000 proteins in low-Hsp90 cells. We observed that 904 proteins changed in their abundance by more than 1.5-fold. When compared with the transcriptome of the same population of cells, two-thirds of the misregulated proteins were observed to be affected posttranscriptionally, of which the majority were downregulated. Further analyses indicated that the downregulated proteins are highly conserved and assume central roles in cellular networks with a high number of protein interacting partners, suggesting that Hsp90 buffers genetic and nongenetic variation through regulating protein network hubs. The downregulated proteins were enriched for essential proteins previously not known to be Hsp90-dependent. Finally, we observed that downregulation of transcription factors and mating pathway components by attenuating Hsp90 function led to decreased target gene expression and pheromone response, respectively, providing a direct link between observed proteome regulation and cellular phenotypes.

GTP-binding-defective ARL4D alters mitochondrial morphology and membrane potential.

ARL4D, ARL4A, and ARL4C are closely related members of the ADP-ribosylation factor/ARF-like protein (ARF/ARL) family of GTPases. All three ARL4 proteins contain nuclear localization signals (NLSs) at their C-termini and are primarily found at the plasma membrane, but they are also present in the nucleus and cytoplasm. ARF function and localization depends on their controlled binding and hydrolysis of GTP. Here we show that GTP-binding-defective ARL4D is targeted to the mitochondria, where it affects mitochondrial morphology and function. We found that a portion of endogenous ARL4D and the GTP-binding-defective ARL4D mutant ARL4D(T35N) reside in the mitochondria. The N-terminal myristoylation of ARL4D(T35N) was required for its localization to mitochondria. The localization of ARL4D(T35N) to the mitochondria reduced the mitochondrial membrane potential (ΔΨm) and caused mitochondrial fragmentation. Furthermore, the C-terminal NLS region of ARL4D(T35N) was required for its effect on the mitochondria. This study is the first to demonstrate that the dysfunctional GTP-binding-defective ARL4D is targeted to mitochondria, where it subsequently alters mitochondrial morphology and membrane potential.