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Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules
Rahaman, Abdur1; Miao, Wei2; Turkewitz, Aaron P.1; Turkewitz, AP, Univ Chicago, Dept Mol Genet & Cell Biol, 920 E 58th St, Chicago, IL 60637 USA
2009-10-01
Source PublicationEUKARYOTIC CELL
ISSN1535-9778
Volume8Issue:10Pages:1575-1583
AbstractDense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, Delta GRT1 Delta GRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in Delta GRT1 Delta GRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from Delta GRT1 Delta GRT2 cells appear less adhesive than those from the wild type.; Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, Delta GRT1 Delta GRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in Delta GRT1 Delta GRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from Delta GRT1 Delta GRT2 cells appear less adhesive than those from the wild type.
SubtypeArticle
KeywordParamecium Maturation Mutants Lattice Polypeptides Trichocysts Exocytosis Expression Genes Cells
Department[Rahaman, Abdur; Turkewitz, Aaron P.] Univ Chicago, Dept Mol Genet & Cell Biol, Chicago, IL 60637 USA; [Miao, Wei] Chinese Acad Sci, Inst Hydrobiol, Wuhan, Peoples R China
Subject AreaMicrobiology
DOI10.1128/EC.00151-09
WOS HeadingsScience & Technology ; Life Sciences & Biomedicine
Funding OrganizationNational Institutes of Health [GM077607] ; National Institutes of Health [GM077607] ; National Institutes of Health [GM077607] ; National Institutes of Health [GM077607]
Indexed BySCI
Language英语
WOS Research AreaMicrobiology
WOS SubjectMicrobiology
WOS IDWOS:000270399300011
WOS KeywordPARAMECIUM ; MATURATION ; MUTANTS ; LATTICE ; POLYPEPTIDES ; TRICHOCYSTS ; EXOCYTOSIS ; EXPRESSION ; GENES ; CELLS
Funding OrganizationNational Institutes of Health [GM077607] ; National Institutes of Health [GM077607] ; National Institutes of Health [GM077607] ; National Institutes of Health [GM077607]
Citation statistics
Cited Times:12[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.ihb.ac.cn/handle/152342/7570
Collection期刊论文
Corresponding AuthorTurkewitz, AP, Univ Chicago, Dept Mol Genet & Cell Biol, 920 E 58th St, Chicago, IL 60637 USA
Affiliation1.Univ Chicago, Dept Mol Genet & Cell Biol, Chicago, IL 60637 USA
2.Chinese Acad Sci, Inst Hydrobiol, Wuhan, Peoples R China
Recommended Citation
GB/T 7714
Rahaman, Abdur,Miao, Wei,Turkewitz, Aaron P.,et al. Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules[J]. EUKARYOTIC CELL,2009,8(10):1575-1583.
APA Rahaman, Abdur,Miao, Wei,Turkewitz, Aaron P.,&Turkewitz, AP, Univ Chicago, Dept Mol Genet & Cell Biol, 920 E 58th St, Chicago, IL 60637 USA.(2009).Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules.EUKARYOTIC CELL,8(10),1575-1583.
MLA Rahaman, Abdur,et al."Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules".EUKARYOTIC CELL 8.10(2009):1575-1583.
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