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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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GFP-Snc1p localizes to early endosomes in the trs130ts2 and -120-8 mutants. Cells were labeled with FM4-64 as described in Materials and methods. FM4-64 was internalized for 5 or 30 min.
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fig5: GFP-Snc1p localizes to early endosomes in the trs130ts2 and -120-8 mutants. Cells were labeled with FM4-64 as described in Materials and methods. FM4-64 was internalized for 5 or 30 min.

Mentions: As shown in Fig. 4 C, GFP-Snc1p–containing structures that accumulate in trs120 and -130 mutants became larger during a 60-min incubation at 37°C. To address whether the enlarged structures are early endosomes or Golgi, we labeled trs130ts2and -120-8 mutant cells that were shifted to 37°C for 30 min with the styryl dye FM4-64. The early endosome is labeled after a brief incubation (5 min) with this dye (Vida and Emr, 1995). At the 5-min time point, the GFP-Snc1p–containing structures were labeled with FM4-64 (Fig. 5), implying that at least some of the Snc1p accumulates in the early endosome at 37°C in the trs130ts2 and -120-8 mutants. At the later time point (30 min), FM4-64 was no longer detected in the GFP-Snc1p–containing structures and instead stained the vacuolar membrane, which was fragmented in both mutants (Fig. 5).


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)

GFP-Snc1p localizes to early endosomes in the trs130ts2 and -120-8 mutants. Cells were labeled with FM4-64 as described in Materials and methods. FM4-64 was internalized for 5 or 30 min.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: GFP-Snc1p localizes to early endosomes in the trs130ts2 and -120-8 mutants. Cells were labeled with FM4-64 as described in Materials and methods. FM4-64 was internalized for 5 or 30 min.
Mentions: As shown in Fig. 4 C, GFP-Snc1p–containing structures that accumulate in trs120 and -130 mutants became larger during a 60-min incubation at 37°C. To address whether the enlarged structures are early endosomes or Golgi, we labeled trs130ts2and -120-8 mutant cells that were shifted to 37°C for 30 min with the styryl dye FM4-64. The early endosome is labeled after a brief incubation (5 min) with this dye (Vida and Emr, 1995). At the 5-min time point, the GFP-Snc1p–containing structures were labeled with FM4-64 (Fig. 5), implying that at least some of the Snc1p accumulates in the early endosome at 37°C in the trs130ts2 and -120-8 mutants. At the later time point (30 min), FM4-64 was no longer detected in the GFP-Snc1p–containing structures and instead stained the vacuolar membrane, which was fragmented in both mutants (Fig. 5).

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