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Mutants in trs120 disrupt traffic from the early endosome to the late Golgi.

Cai H, Zhang Y, Pypaert M, Walker L, Ferro-Novick S - J. Cell Biol. (2005)

Bottom Line: Transport protein particle (TRAPP), a large complex that mediates membrane traffic, is found in two forms (TRAPPI and -II).Surprisingly, we report that mutations in trs120 do not block general secretion.Furthermore, we demonstrate that Trs120p largely colocalizes with the late Golgi marker Sec7p.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06519, USA.

ABSTRACT
Transport protein particle (TRAPP), a large complex that mediates membrane traffic, is found in two forms (TRAPPI and -II). Both complexes share seven subunits, whereas three subunits (Trs130p, -120p, and -65p) are specific to TRAPPII. Previous studies have shown that mutations in the TRAPPII-specific gene trs130 block traffic through or from the Golgi. Surprisingly, we report that mutations in trs120 do not block general secretion. Instead, trs120 mutants accumulate aberrant membrane structures that resemble Berkeley bodies and disrupt the traffic of proteins that recycle through the early endosome. Mutants defective in recycling also display a defect in the localization of coat protein I (COPI) subunits, implying that Trs120p may participate in a COPI-dependent trafficking step on the early endosomal pathway. Furthermore, we demonstrate that Trs120p largely colocalizes with the late Golgi marker Sec7p. Our findings imply that Trs120p is required for vesicle traffic from the early endosome to the late Golgi.

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Related in: MedlinePlus

Mutants in trs120 and -130 are defective in the trafficking of Chs3p-GFP. Chs3p-GFP was examined in wild-type and mutant cells that were grown at 25°C or shifted to 37°C for 30 min. Arrows point to bud necks and incipient bud sites, which are visible in the differential interference contrast (DIC) image.
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fig6: Mutants in trs120 and -130 are defective in the trafficking of Chs3p-GFP. Chs3p-GFP was examined in wild-type and mutant cells that were grown at 25°C or shifted to 37°C for 30 min. Arrows point to bud necks and incipient bud sites, which are visible in the differential interference contrast (DIC) image.

Mentions: To determine whether another marker protein that travels through the early endosome is also defective in these trs120 and -130 mutants, we analyzed the cell surface enzyme Chs3p. Chs3p follows a recycling pathway that is similar to Snc1p. It localizes to the mother-bud junction, the cell surface, and punctate intracellular structures called chitosomes (Chuang and Schekman, 1996; Valdivia et al., 2002). To monitor the recycling of Chs3p, we grew wild-type and mutant cells at the permissive temperature or shifted them to 37°C for 30 min. Quantitation of ∼100–150 cells revealed that at 37°C Chs3p-GFP localized to the mother–bud neck region in ∼51% of wild-type cells. A dramatic decrease in the targeting of Chs3p-GFP to the bud neck was observed in the trs130ts2 (8%), -120-2 (10.5%), and -120-8 (9%) mutants at this temperature, whereas a modest decrease was seen in the trs120-4 (29%) mutant (Fig. 6). The trs120-2 mutant also displayed a partial defect (30%) at 25°C, whereas no defect was observed in the trs130ts2, -120-4, and -120-8 mutants at this temperature (Fig. 6). These findings indicate that mutants in trs120 and -130 display defects in the targeting of Chs3p to the bud neck. Furthermore, the temperature dependence and the severity of the defect for each of the affected mutants was the same as observed for GFP-Snc1p.


Mutants in trs120 disrupt traffic from the early endosome to the late Golgi.

Cai H, Zhang Y, Pypaert M, Walker L, Ferro-Novick S - J. Cell Biol. (2005)

Mutants in trs120 and -130 are defective in the trafficking of Chs3p-GFP. Chs3p-GFP was examined in wild-type and mutant cells that were grown at 25°C or shifted to 37°C for 30 min. Arrows point to bud necks and incipient bud sites, which are visible in the differential interference contrast (DIC) image.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171297&req=5

fig6: Mutants in trs120 and -130 are defective in the trafficking of Chs3p-GFP. Chs3p-GFP was examined in wild-type and mutant cells that were grown at 25°C or shifted to 37°C for 30 min. Arrows point to bud necks and incipient bud sites, which are visible in the differential interference contrast (DIC) image.
Mentions: To determine whether another marker protein that travels through the early endosome is also defective in these trs120 and -130 mutants, we analyzed the cell surface enzyme Chs3p. Chs3p follows a recycling pathway that is similar to Snc1p. It localizes to the mother-bud junction, the cell surface, and punctate intracellular structures called chitosomes (Chuang and Schekman, 1996; Valdivia et al., 2002). To monitor the recycling of Chs3p, we grew wild-type and mutant cells at the permissive temperature or shifted them to 37°C for 30 min. Quantitation of ∼100–150 cells revealed that at 37°C Chs3p-GFP localized to the mother–bud neck region in ∼51% of wild-type cells. A dramatic decrease in the targeting of Chs3p-GFP to the bud neck was observed in the trs130ts2 (8%), -120-2 (10.5%), and -120-8 (9%) mutants at this temperature, whereas a modest decrease was seen in the trs120-4 (29%) mutant (Fig. 6). The trs120-2 mutant also displayed a partial defect (30%) at 25°C, whereas no defect was observed in the trs130ts2, -120-4, and -120-8 mutants at this temperature (Fig. 6). These findings indicate that mutants in trs120 and -130 display defects in the targeting of Chs3p to the bud neck. Furthermore, the temperature dependence and the severity of the defect for each of the affected mutants was the same as observed for GFP-Snc1p.

Bottom Line: Transport protein particle (TRAPP), a large complex that mediates membrane traffic, is found in two forms (TRAPPI and -II).Surprisingly, we report that mutations in trs120 do not block general secretion.Furthermore, we demonstrate that Trs120p largely colocalizes with the late Golgi marker Sec7p.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06519, USA.

ABSTRACT
Transport protein particle (TRAPP), a large complex that mediates membrane traffic, is found in two forms (TRAPPI and -II). Both complexes share seven subunits, whereas three subunits (Trs130p, -120p, and -65p) are specific to TRAPPII. Previous studies have shown that mutations in the TRAPPII-specific gene trs130 block traffic through or from the Golgi. Surprisingly, we report that mutations in trs120 do not block general secretion. Instead, trs120 mutants accumulate aberrant membrane structures that resemble Berkeley bodies and disrupt the traffic of proteins that recycle through the early endosome. Mutants defective in recycling also display a defect in the localization of coat protein I (COPI) subunits, implying that Trs120p may participate in a COPI-dependent trafficking step on the early endosomal pathway. Furthermore, we demonstrate that Trs120p largely colocalizes with the late Golgi marker Sec7p. Our findings imply that Trs120p is required for vesicle traffic from the early endosome to the late Golgi.

Show MeSH
Related in: MedlinePlus