An endosomal syntaxin and the AP-3 complex are required for formation and maturation of candidate lysosome-related secretory organelles (mucocysts) in<i>Tetrahymena thermophila</i>

Kaur, Harsimran; Sparvoli, Daniela; Osakada, Hiroko; Iwamoto, Mutsuo; Haraguchi, Tokuko; Turkewitz, Aaron P.

doi:10.1091/mbc.e17-01-0018

Cited by 19 publications

(40 citation statements)

References 99 publications

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“…Significantly, mucocysts are not multivesicular, unlike Apicomplexan rhoptries. However, the delivery to mucocysts of Cth3p and Grt/Igr proteins, but not the Grl proteins, requires the sortilin/VPS10 receptor, Sor4p, as well as an endosomal SNARE (Soluble NSF attachment protein receptor), Stx7l1p (Syntaxin 7-like) [47,48]. These results suggested that extrusomes in ciliates may depend on LRO-related mechanisms that bear fundamental similarities with those used in apicomplexans.…”

Section: Lro Formation Involves Cytoplasmic and Membrane Proteins Incmentioning

confidence: 94%

An evolutionary switch in the specificity of an endosomal CORVET tether underlies formation of regulated secretory vesicles in the ciliateTetrahymena thermophila

Sparvoli

Richardson

Osakada

et al. 2017

Preprint

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SummaryIn the endocytic pathway of animals, two related complexes, called CORVET (Class C Core Vacuole/Endosome Transport) and HOPS (Homotypic fusion and protein sorting), act as both tethers and fusion factors for early and late endosomes, respectively. Mutations in CORVET or HOPS lead to trafficking defects and contribute to human disease including immune dysfunction. HOPS and CORVET are conserved throughout eukaryotes but remarkably, in the ciliate Tetrahymena thermophila, the HOPS-specific subunits are absent while CORVET-specific subunits have proliferated. VPS8 (Vacuolar Protein Sorting), a CORVET subunit, expanded to 6 paralogs in Tetrahymena. This expansion correlated with loss of HOPS within a ciliate subgroup including the Oligohymenophorea, which contains Tetrahymena. As uncovered via forward genetics, a single VPS8 paralog in Tetrahymena (VPS8A) is required to synthesize prominent secretory granules called mucocysts. More specifically, ∆vps8a cells fail to deliver a subset of cargo proteins to developing mucocysts, instead accumulating that cargo in vesicles also bearing the mucocyst sorting receptor, Sor4p. Surprisingly, although this transport step relies on CORVET, it does not appear to involve early endosomes. Instead, Vps8a associates with the late endosomal/lysosomal marker Rab7, indicating target specificity switching occurred in CORVET subunits during the evolution of ciliates. Mucocysts belong to a markedly diverse and understudied class of protist secretory organelles called extrusomes. Our results underscore that biogenesis of mucocysts depends on endolysosomal trafficking, revealing parallels with invasive organelles in apicomplexan parasites and suggesting that a wide array of secretory adaptations in protists, like in animals, depend on mechanisms related to lysosome biogenesis.AbbreviationsLRO(Lysosome-related organelle)HOPS(homotypic fusion and protein sorting complex)CORVET(Class C core Vacuole/Endosome Transport)VPS(vacuolar protein sorting)GRL(granule lattice)GRT(granule tip)Igr(Induced upon granule regeneration)SNARE(Soluble NSF attachment protein receptor)LECA(last eukaryotic common ancestor)

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Section: Lro Formation Involves Cytoplasmic and Membrane Proteins Incmentioning

confidence: 94%

An evolutionary switch in the specificity of an endosomal CORVET tether underlies formation of regulated secretory vesicles in the ciliateTetrahymena thermophila

Sparvoli

Richardson

Osakada

et al. 2017

Preprint

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“…Tetrahymena transformants were generated and selected after biolistic transformation as previously described (Kaur et al, 2017;Sparvoli et al, 2018). Transformants were serially transferred 6x/week in increasing concentrations of drug and decreasing concentrations of CdCl 2 (up to 2 mg/ml of paromomycin and 0.1 μg/ml CdCl 2 ; up to 18-21 μg/ml of cycloheximide and 1 μg/ml CdCl 2 ; up to 90 μg/ml of blasticidin and 0.1 μg/ml…”

Section: Biolistic Transformationmentioning

confidence: 99%

“…The expression of Rab7 was induced by adding 1 μg/ml CdCl 2 to the S medium. Cells were immobilized in thin 3% low melting agarose gel pads, as described previously (Kaur et al, 2017), and imaged within 15 minutes. Z stack images (12 stacks along the z axis at 0.5 μm intervals) and time-lapse videos (30 frames at 1.24 sec interval for mNeon-tagged Vps8 paralogs; 200 frames at 0.17 sec/interval for Vps8c-mNeon/mCherry-Rab7) were collected at room temperature with a Marianas Yokogawa type spinning disk inverted confocal microscope, 100X oil with NA=1.45, equipped with two photometrics Evolve back-thinned EM-CCD cameras, with Slidebook6 software (Zeiss, Intelligent Imaging Innovations, Denver, CO).…”

Section: Live Cell Imagingmentioning

confidence: 99%

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Diversification of CORVET tethers facilitates transport complexity inTetrahymena thermophila

Sparvoli

Zoltner

Field

et al. 2019

Preprint

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In endolysosomal networks, two hetero-hexameric tethers called HOPS and CORVET are found widely throughout eukaryotes. The unicellular ciliate Tetrahymena thermophila possesses elaborate endolysosomal structures, but curiously both it and related protozoa lack the HOPS tether and several other trafficking genes while retaining the related CORVET complex. Tetrahymena encodes multiple paralogs of most CORVET subunits, which assemble into six distinct complexes. Each complex has a unique subunit composition and, significantly, shows unique localization, indicating participation in distinct pathways. One pair of complexes differ by a single subunit (Vps8), but have late endosomal vs. recycling endosome locations. While Vps8 subunits are thus prime determinants for targeting and functional specificity, determinants exist on all subunits except Vps11. This unprecedented expansion and diversification of CORVET provides a potent example of tether flexibility, and illustrates how 'backfilling' following secondary losses of trafficking genes can provide a mechanism for evolution of new pathways. 3

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“…These include a subunit of the AP3 complex and a syntaxin in the STX7 subfamily. Subsequent functional analysis of these genes showed that they are both essential for mucocyst formation, providing the best evidence to date that mucocysts are lysosome-related organelles [31]. The CDH report for this CTH3 query is attached as Supplementary File 4.…”

Section: Illustrative Examplesmentioning

confidence: 99%

The Co-regulation Data Harvester: Automating gene annotation starting from a transcriptome database

Tsypin

Turkewitz

2017

SoftwareX

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Identifying co-regulated genes provides a useful approach for defining pathway-specific machinery in an organism. To be efficient, this approach relies on thorough genome annotation, a process much slower than genome sequencing per se. Tetrahymena thermophila, a unicellular eukaryote, has been a useful model organism and has a fully sequenced but sparsely annotated genome. One important resource for studying this organism has been an online transcriptomic database. We have developed an automated approach to gene annotation in the context of transcriptome data in T. thermophila, called the Co-regulation Data Harvester (CDH). Beginning with a gene of interest, the CDH identifies co-regulated genes by accessing the Tetrahymena transcriptome database. It then identifies their closely related genes (orthologs) in other organisms by using reciprocal BLAST searches. Finally, it collates the annotations of those orthologs’ functions, which provides the user with information to help predict the cellular role of the initial query. The CDH, which is freely available, represents a powerful new tool for analyzing cell biological pathways in Tetrahymena. Moreover, to the extent that genes and pathways are conserved between organisms, the inferences obtained via the CDH should be relevant, and can be explored, in many other systems.

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An endosomal syntaxin and the AP-3 complex are required for formation and maturation of candidate lysosome-related secretory organelles (mucocysts) inTetrahymena thermophila

Cited by 19 publications

References 99 publications

An evolutionary switch in the specificity of an endosomal CORVET tether underlies formation of regulated secretory vesicles in the ciliateTetrahymena thermophila

An evolutionary switch in the specificity of an endosomal CORVET tether underlies formation of regulated secretory vesicles in the ciliateTetrahymena thermophila

Diversification of CORVET tethers facilitates transport complexity inTetrahymena thermophila

The Co-regulation Data Harvester: Automating gene annotation starting from a transcriptome database

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