scholarly journals The Fission Yeast spo14 + Gene Encoding a Functional Homologue of Budding Yeast Sec12 Is Required for the Development of Forespore Membranes

2003 ◽  
Vol 14 (3) ◽  
pp. 1109-1124 ◽  
Author(s):  
Michiko Nakamura-Kubo ◽  
Taro Nakamura ◽  
Aiko Hirata ◽  
Chikashi Shimoda
Keyword(s):  
Secretory Pathway ◽  
Protein Transport ◽  
Membrane Vesicles ◽  
Spindle Pole ◽  
Nucleotide Exchange ◽  
Gene Encoding ◽  
Single Nucleotide Change ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Cold Sensitive

The Schizosaccharomyces pombe spo14-B221 mutant was originally isolated as a sporulation-deficient mutant. However, thespo14 + gene is essential for cell viability and growth. spo14 + is identical to the previously characterizedstl1 + gene encoding a putative homologue of Saccharomyces cerevisiae Sec12, which is essential for protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus. In the spo14 mutant cells, ER-like membranes were accumulated beneath the plasma membrane and the ER/Golgi shuttling protein Rer1 remained in the ER. Sec12 is a guanine nucleotide exchange factor for the Sar1 GTPase. Overproduction ofpsr1 + coding for an S. pombe Sar1 homologue suppressed both the sporulation defect ofspo14-B221 and cold-sensitive growth of newly isolatedspo14-6 and spo14-7 mutants. These results indicate that Spo14 is involved in early steps of the protein secretory pathway. The spo14-B221 allele carries a single nucleotide change in the branch point consensus of the fifth intron, which reduces the abundance of the spo14 mRNA. During meiosis II, the forespore membrane was initiated near spindle pole bodies; however, subsequent extension of the membrane was arrested before its closure into a sac. We conclude that Spo14 is responsible for the assembly of the forespore membrane by supplying membrane vesicles.

scholarly journals mTrs130 Is a Component of a Mammalian TRAPPII Complex, a Rab1 GEF That Binds to COPI-coated Vesicles

2009 ◽  
Vol 20 (19) ◽  
pp. 4205-4215 ◽  
Author(s):  
Akinori Yamasaki ◽  
Shekar Menon ◽  
Sidney Yu ◽  
Jemima Barrowman ◽  
Timo Meerloo ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Secretory Pathway ◽  
Coated Vesicles ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Golgi Compartment ◽  
A Subunit ◽  
Protein Particle ◽  
First Time

The GTPase Rab1 regulates endoplasmic reticulum-Golgi and early Golgi traffic. The guanine nucleotide exchange factor (GEF) or factors that activate Rab1 at these stages of the secretory pathway are currently unknown. Trs130p is a subunit of the yeast TRAPPII (transport protein particle II) complex, a multisubunit tethering complex that is a GEF for the Rab1 homologue Ypt1p. Here, we show that mammalian Trs130 (mTrs130) is a component of an analogous TRAPP complex in mammalian cells, and we describe for the first time the role that this complex plays in membrane traffic. mTRAPPII is enriched on COPI (Coat Protein I)-coated vesicles and buds, but not Golgi cisternae, and it specifically activates Rab1. In addition, we find that mTRAPPII binds to γ1COP, a COPI coat adaptor subunit. The depletion of mTrs130 by short hairpin RNA leads to an increase of vesicles in the vicinity of the Golgi and the accumulation of cargo in an early Golgi compartment. We propose that mTRAPPII is a Rab1 GEF that tethers COPI-coated vesicles to early Golgi membranes.

scholarly journals Checkpoint control of mitotic exit—do budding yeast mind the GAP?

2006 ◽  
Vol 172 (3) ◽  
pp. 331-333 ◽  
Author(s):  
John A. Cooper ◽  
Scott A. Nelson
Keyword(s):  
Budding Yeast ◽  
Spindle Pole ◽  
Small Gtpase ◽  
Mitotic Exit ◽  
Cell Cycle Checkpoints ◽  
Nucleotide Exchange ◽  
Checkpoint Control ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Spindle Pole Bodies

Cell cycle checkpoints can delay mitotic exit in budding yeast. The master controller is the small GTPase Tem1, with inputs from a proposed guanine nucleotide exchange factor (GEF), Lte1, and a GTPase-activating protein (GAP), Bub2/Bfa1. In this issue, Fraschini et al. (p. 335) show that GAP activity of Bub2/Bfa1 appears to be dispensable for inactivation of Tem1 in cells. Their results call into question the GTP/GDP switch model for Tem1 activity, as have other results in the past. The paper also focuses attention on the two spindle pole bodies as potential sites for regulation of Tem1.

scholarly journals Sar1 promotes vesicle budding from the endoplasmic reticulum but not Golgi compartments.

1994 ◽  
Vol 125 (1) ◽  
pp. 51-65 ◽  
Author(s):  
O Kuge ◽  
C Dascher ◽  
L Orci ◽  
T Rowe ◽  
M Amherdt ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Transitional Region ◽  
Nucleotide Exchange ◽  
New Members ◽  
Vesicle Budding ◽  
Guanine Nucleotide Exchange ◽  
Vesicular Carriers

Two new members (Sar1a and Sar1b) of the SAR1 gene family have been identified in mammalian cells. Using immunoelectron microscopy, Sar1 was found to be restricted to the transitional region where the protein was enriched 20-40-fold in vesicular carriers mediating ER to Golgi traffic. Biochemical analysis revealed that Sar1 was essential for an early step in vesicle budding. A Sar1-specific antibody potently inhibited export of vesicular stomatitis virus glycoprotein (VSV-G) from the ER in vitro. Consistent with the role of guanine nucleotide exchange in Sar1 function, a trans-dominant mutant (Sar1a[T39N]) with a preferential affinity for GDP also strongly inhibited vesicle budding from the ER. In contrast, Sar1 was not found to be required for the transport of VSV-G between sequential Golgi compartments, suggesting that components active in formation of vesicular carriers mediating ER to Golgi traffic may differ, at least in part, from those involved in intra-Golgi transport. The requirement for novel components at different stages of the secretory pathway may reflect the recently recognized differences in protein transport between the Golgi stacks as opposed to the selective sorting and concentration of protein during export from the ER.

scholarly journals Trappc9 deficiency in mice impairs learning and memory by causing imbalance of dopamine D1 and D2 neurons

2020 ◽  
Vol 6 (47) ◽  
pp. eabb7781
Author(s):  
Yuting Ke ◽  
Meiqian Weng ◽  
Gaurav Chhetri ◽  
Muhammad Usman ◽  
Yan Li ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
D2 Receptor ◽  
Brain Structures ◽  
Rab Proteins ◽  
Nucleotide Exchange ◽  
Gene Encoding ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
The Brain ◽  
Deficient Mice

Genetic mutations in the gene encoding transport protein particle complex 9 (trappc9), a subunit of TRAPP that acts as a guanine nucleotide exchange factor for rab proteins, cause intellectual disability with brain structural malformations by elusive mechanisms. Here, we report that trappc9-deficient mice exhibit a broad range of behavioral deficits and postnatal delay in growth of the brain. Contrary to volume decline of various brain structures, the striatum of trappc9 null mice was enlarged. An imbalance existed between dopamine D1 and D2 receptor containing neurons in the brain of trappc9-deficient mice; pharmacological manipulation of dopamine receptors improved performances of trappc9 null mice to levels of wild-type mice on cognitive tasks. Loss of trappc9 compromised the activation of rab11 in the brain and resulted in retardation of endocytic receptor recycling in neurons. Our study elicits a pathogenic mechanism and a potential treatment for trappc9-linked disorders including intellectual disability.

scholarly journals The TRAPP Complex Is a Nucleotide Exchanger for Ypt1 and Ypt31/32

2000 ◽  
Vol 11 (12) ◽  
pp. 4403-4411 ◽  
Author(s):  
Sara Jones ◽  
Christina Newman ◽  
Fengli Liu ◽  
Nava Segev
Keyword(s):  
Protein Complex ◽  
Protein Transport ◽  
Apparent Molecular Weight ◽  
Yeast Cells ◽  
Mutant Protein ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Exocytic Pathway

In yeast, the Ypt1 GTPase is required for ER-to-cis-Golgi and cis-to-medial-Golgi protein transport, while Ypt31/32 are a functional pair of GTPases essential for exit from the trans-Golgi. We have previously identified a Ypt1 guanine nucleotide exchange factor (GEF) activity and characterized it as a large membrane-associated protein complex that localizes to the Golgi and can be extracted from the membrane by salt, but not by detergent. TRAPP is a large protein complex that is required for ER-to-Golgi transport and that has properties similar to those of Ypt1 GEF. Here we show that TRAPP has Ypt1 GEF activity. GST-tagged Bet3p or Bet5p, two of the TRAPP subunits, were expressed in yeast cells and were precipitated by glutathione-agarose (GA) beads. The resulting precipitates can stimulate both GDP release and GTP uptake by Ypt1p. The majority of the Ypt1 GEF activity associated with the GST-Bet3p precipitate has an apparent molecular weight of > 670 kDa, indicating that the GEF activity resides in the TRAPP complex. Surprisingly, TRAPP can also stimulate nucleotide exchange on the Ypt31/32 GTPases, but not on Sec4p, a Ypt-family GTPase required for the last step of the exocytic pathway. Like the previously characterized Ypt1 GEF, the TRAPP Ypt1-GEF activity can be inhibited by the nucleotide-free Ypt1-D124N mutant protein. This mutant protein also inhibits the Ypt32 GEF activity of TRAPP. Coprecipitation and overexpression studies suggest that TRAPP can act as a GEF for Ypt1 and Ypt31/32 in vivo. These data suggest the exciting possibility that a GEF complex common to Ypt1 and Ypt31/32 might coordinate the function of these GTPases in entry into and exit from the Golgi.

scholarly journals Effects of Picornavirus 3A Proteins on Protein Transport and GBF1-Dependent COP-I Recruitment

2006 ◽  
Vol 80 (23) ◽  
pp. 11852-11860 ◽  
Author(s):  
Els Wessels ◽  
Daniël Duijsings ◽  
Kjerstin H. W. Lanke ◽  
Sander H. J. van Dooren ◽  
Catherine L. Jackson ◽  
...  
Keyword(s):  
Protein Transport ◽  
Hepatitis A Virus ◽  
Foot And Mouth Disease ◽  
Underlying Mechanism ◽  
Encephalomyocarditis Virus ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Mouth Disease Virus ◽  
The Family

ABSTRACT The 3A protein of the coxsackievirus B3 (CVB3), an enterovirus that belongs to the family of the picornaviruses, inhibits endoplasmic reticulum-to-Golgi transport. Recently, we elucidated the underlying mechanism by showing that CVB3 3A interferes with ADP-ribosylation factor 1 (Arf1)-dependent COP-I recruitment to membranes by binding and inhibiting the function of GBF1, a guanine nucleotide exchange factor that is required for the activation of Arf1 (E. Wessels et al., Dev. Cell 11:191-201, 2006). Here, we show that the 3A protein of poliovirus, another enterovirus, is also able to interfere with COP-I recruitment through the same mechanism. No interference with protein transport or COP-I recruitment was observed for the 3A proteins of any of the other picornaviruses tested here (human rhinovirus [HRV], encephalomyocarditis virus, foot-and-mouth disease virus, and hepatitis A virus). We show that the 3A proteins of HRV, which are the most closely related to the enteroviruses, are unable to inhibit COP-I recruitment, due to a reduced ability to bind GBF1. When the N-terminal residues of the HRV 3A proteins are replaced by those of CVB3 3A, chimeric proteins are produced that have gained the ability to bind GBF1 and, by consequence, to inhibit protein transport. These results show that the N terminus of the CVB3 3A protein is important for binding of GBF1 and its transport-inhibiting function. Taken together, our data demonstrate that the activity of the enterovirus 3A protein to inhibit GBF1-dependent COP-I recruitment is unique among the picornaviruses.

scholarly journals Structure and mechanism of TRAPPIII-mediated Rab1 activation

2020 ◽  
Author(s):  
Aaron M.N. Joiner ◽  
Ben P. Phillips ◽  
Kumar Yugandhar ◽  
Ethan J. Sanford ◽  
Marcus B. Smolka ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Membrane Surface ◽  
Regulatory Subunit ◽  
Amphipathic Helix ◽  
Nucleotide Exchange ◽  
Early Secretory Pathway ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Α Helix ◽  
And Function

ABSTRACTThe GTPase Rab1 is a master regulator of both the early secretory pathway and autophagy. Rab1 activation is controlled by its GEF (guanine nucleotide exchange factor), the multi-subunit TRAPPIII complex. The Trs85 regulatory subunit is critical for robust activation of Rab1 but its mechanistic role within the complex has remained unclear. Here we report the cryo-EM structure of the intact yeast TRAPPIII complex bound to its substrate Rab1/Ypt1. The orientation of the Rab1/Ypt1 hypervariable domain when bound to the complex leads to a model for how TRAPPIII associates with and activates Rab1/Ypt1 at the membrane surface. We identify a conserved amphipathic α-helix motif within Trs85 and demonstrate that this helix is required for stable membrane binding and Rab1/Ypt1 activation by TRAPPIII. Taken together, our results provide a comprehensive analysis of the structure and function of the yeast TRAPPIII complex and reveal that the key function of Trs85 is to serve as a membrane anchor, via its amphipathic helix, for the entire TRAPPIII complex.

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