Biology subjects

He, C. Y.

Publications and source records attributed to He, C. Y..

7 recordsLinked to original sources

bioRxiv2025

Spatiotemporal regulation of ciliary outer dynein arm biogenesis and the role of PIH homologs

Outer Dynein Arm complex (ODA) powers motile cilia that are indispensable for fundamental processes, including embryogenesis, reproduction, and respiration. The ODA subunits: heavy (HC), intermediate (IC), and light chains (LC), are known to preassemble in the cytoplasm with the help of Dynein Axonemal Assembly Factors (DNAAFs). The mechanistic details underlying functional ODA assembly and the specific roles of DNAAFs in orchestrating subunit translation, folding, and assembly are still poorly defined. Using Trypanosoma brucei as a model, we showed that ODA preassembly is coupled to HC translation, during which ICs post-translationally associate with translating HCs to form co-translational assembly sites. PIH1D1, a DNAAF and a PIH family protein, concentrates at these cotranslational assembly sites. Without PIH1D1, HC protein levels are reduced, leaving the IC-LC complex stranded in the cytoplasm. We propose that PIH1D1 generates specialised compartments to assist the co-translational folding of HCs and enable their assembly with the other ODA subunits. Our study highlights spatial compartmentalization as a conserved strategy that interweaves translation, folding, and assembly to ensure ordered and timely ODA formation during ciliogenesis.

cell biology↗

bioRxiv2024

Rab2B promotes chaperonin-mediated actin folding and prevents developmental transcription reprogramming and quiescence in trypanosomes

The Rab family of small GTPases are regulators of intracellular membrane trafficking. Rab2B, a Golgi-resident Rab GTPase, has been shown to function in ER-Golgi transport and autophagosome-lysosome fusion in mammalian cells and Drosophila. In Trypanosoma brucei, the autophagy-related function of Rab2B was conserved and depletion of Rab2B blocked autophagosome-lysosome fusion. Intriguingly, depletion of Rab2B induced differentiation of T. brucei from a proliferative slender form to a quiescent stumpy form, a step crucial for parasite transmission. Chaperonin CCT/TRiC was identified as an effector of Rab2B. Depletion of CCT/TRiC subunits or actin (a known CCT/TRiC substrate), or blocking actin polymerisation with Latrunculin A all triggered differentiation, suggesting a role of Rab2B on CCT/TRiC-mediated actin folding. Using an actin chromobody, we identified a pool of nuclear actin that is crucial for transcription reprogramming and life cycle differentiation in T. brucei. The study revealed a function of Rab2B and actin in T. brucei transcription reprogramming leading to cell differentiation, and an unexpected role of Rab2B and CCT/TRiC mediated actin folding.

cell biology↗

bioRxiv2023

Arl3 regulates ODA16-mediated intraflagellar transport in motile cilia biogenesis

Arl13b and Arl3 are ciliary GTPases implicated in human Joubert Syndrome, affecting ciliary membrane and axoneme organization. Although the mechanism of Arl13b as a guanine nucleotide exchange factor (GEF) of Arl3 and the function of Arl13b and Arl3 in ciliary membrane protein transport are well established, their role in axoneme biogenesis is unclear. In Trypanosoma brucei, TbArl13 acts as a GEF for two distinct TbArl3 proteins, TbArl3A and TbArl3C. Here, we identified the T. brucei homolog of ODA16, a cargo adapter facilitating intraflagellar transport (IFT) of motile ciliary components, as an effector of both TbArl3A and TbArl3C. Depletion of TbArl3 GTPases stabilized TbODA16 interaction with IFT, while active TbArl3 variants displaced TbODA16 from IFT, demonstrating a mechanism of TbArl3 in motile ciliary cargo transport. One-sentence summaryArl3 acts as a displacement factor and releases ODA16 from IFT

cell biology↗

bioRxiv2021

Spatial regulation of AMPK signaling revealed by a sensitive kinase activity reporter

AMP-activated protein kinase (AMPK) is a master regulator of cellular energetics which coordinates metabolism by phosphorylating a plethora of substrates throughout the cell. But whether AMPK activity is regulated at different subcellular locations to provide precise spatial and temporal control over metabolism is unclear. Genetically encoded AMPK activity reporters (AMPKAR) have provided a window into spatial AMPK activity, but the limited dynamic range of current AMPKARs hinders detailed study. To monitor the dynamic activity of AMPK with high sensitivity, we developed a single-fluorophore AMPK activity reporter (ExRai AMPKAR) that exhibits an excitation ratiometric fluorescence change upon phosphorylation by AMPK, with over 3-fold greater response compared to previous AMPKARs. Using subcellularly localized ExRai AMPKAR, we found that the activity of AMPK at the lysosome and mitochondria are differentially regulated. While different activating conditions, irrespective of their effects on ATP, robustly yet gradually increase mitochondrial AMPK activity, lysosomal AMPK activity accumulates with much faster kinetics. Genetic deletion of the canonical upstream kinase liver kinase B1 (LKB1) resulted in slower AMPK activity at lysosomes but did not affect the response amplitude at either location, in sharp contrast to the necessity of LKB1 for maximal cytoplasmic AMPK activity. We further discovered AMPK activity in the nucleus, which resulted from LKB1-mediated cytoplasmic activation of AMPK followed by nuclear shuttling. Thus, a new, sensitive reporter for AMPK activity, ExRai AMPKAR, in complement with mathematical and biophysical methods, captured subcellular AMPK activity dynamics in living cells and unveiled complex regulation of AMPK signaling within subcellular compartments.

molecular biology↗

bioRxiv2021

The Chloroflexi supergroup is metabolically diverse and representatives have novel genes for non-photosynthesis based CO2 fixation

The Chloroflexi superphylum have been investigated primarily from the perspective of reductive dehalogenation of toxic compounds, anaerobic photosynthesis and wastewater treatment, but remain relatively little studied compared to their close relatives within the larger Terrabacteria group, including Cyanobacteria, Actinobacteria, and Firmicutes. Here, we conducted a detailed phylogenetic analysis of the phylum Chloroflexota, the phylogenetically proximal candidate phylum Dormibacteraeota, and a newly defined sibling phylum proposed in the current study, Eulabeiota. These groups routinely root together in phylogenomic analyses, and constitute the Chloroflexi supergroup. Chemoautotrophy is widespread in Chloroflexi. Two Form I Rubisco ancestral subtypes that both lack the small subunit are prevalent in ca. Eulabeiota and Chloroflexota, suggesting that the predominant modern pathway for CO2 fixation evolved in these groups. The single subunit Form I Rubiscos are inferred to have evolved prior to oxygenation of the Earths atmosphere and now predominantly occur in anaerobes. Prevalent in both Chloroflexota and ca. Eulabeiota are capacities related to aerobic oxidation of gases, especially CO and H2. In fact, aerobic and anaerobic CO dehydrogenases are widespread throughout every class-level lineage, whereas traits such as denitrification and reductive dehalogenation are heterogeneously distributed across the supergroup. Interestingly, some Chloroflexota have a novel clade of group 3 NiFe hydrogenases that is phylogenetically distinct from previously reported groups. Overall, the analyses underline the very high level of metabolic diversity in the Chloroflexi supergroup, suggesting the ancestral metabolic platform for this group enabled highly varied adaptation to ecosystems that appeared in the aerobic world.

microbiology↗

bioRxiv2020

Huge and variable diversity of episymbiotic CPR bacteria and DPANN archaea in groundwater ecosystems

Candidate Phyla Radiation (CPR) bacteria and DPANN archaea are uncultivated, small-celled symbionts often detected in groundwater. However, variations in CPR/DPANN organism abundance, distribution, taxonomic diversity, and degree/nature of host association with groundwater chemistry remain understudied. Here, we performed genome-resolved metagenomic characterization of one agriculturally-impacted and seven pristine groundwater microbial communities in California, recovering 746 dereplicated CPR and DPANN genomes. Our finding of up to 31% CPR bacteria and 4% DPANN archaea in the pristine sites, which serve as local sources of drinking water, may hold health relevance, given growing awareness of the presence of CPR/DPANN organisms in human microbiomes and their association with disease. There is little species-level genome overlap across groundwater sites, indicating that CPR and DPANN communities are highly differentiated according to host populations and physicochemical conditions. Cryo-TEM imaging and genomic analyses indicate that CPR growth may be stimulated by attachment to the surface of host cells, and identified CPR and DPANN lineages with particularly prevalent and/or resilient host cell attachment. These results establish the huge but site-specific diversity of CPR bacteria and DPANN archaea coexisting with diverse hosts in groundwater aquifers, and raise important questions about potential impacts on human health.

microbiology↗

bioRxiv2020

Flagellar targeting of an arginine kinase requires the conserved Lipidated Intraflagellar Transport (LIFT) pathway in Trypanosoma brucei

Both intraflagellar transport (IFT) and lipidated intraflagellar transport (LIFT) pathways are essential for cilia/flagella biogenesis, motility and sensory functions. In the LIFT pathway, lipidated cargoes are transported into the cilia through the coordinated actions of cargo carrier proteins such as Unc119 or PDE6{delta}, as well as small GTPases Arl13b and Arl3 in the cilium. Our previous studies revealed a single Arl13b ortholog in the evolutionarily divergent Trypanosoma brucei. TbArl13 catalyses two TbArl3 homologs, TbArl3A and TbArl3C, suggesting the presence of a conserved LIFT pathway in these protozoan parasites. Only a single homolog to the cargo carrier protein Unc119 was identified in T. brucei genome, but its function in lipidated protein transport has not been characterized. In this study, we exploited the proximity-based biotinylation approach to identify binding partners of TbUnc119. We showed that TbUnc119 binds to a flagellar arginine kinase TbAK3 in a myristoylation-dependent manner and is responsible for its targeting and enrichment in the flagellum. Interestingly, only TbArl3A, but not TbArl3C interacts with TbUnc119 in a GTP-dependant manner, suggesting functional specialization of Arl3-GTPases in T. brucei. This study establishes the function of TbUnc119 as a myristoylated cargo carrier and supports the presence of a conserved LIFT pathway in T. brucei.

cell biology↗