Protein Transport into Mitochondria: Cytosolic Factors Which Operate During and After Translation in Protein Trafficking

1996 ◽  
pp. 13-32
Author(s):  
Lisa Estey ◽  
Michael G. Douglas
Keyword(s):  
Protein Trafficking ◽  
Protein Transport ◽  
Cytosolic Factors

scholarly journals Peroxisome extensions deliver the Arabidopsis SDP1 lipase to oil bodies

2015 ◽  
Vol 112 (13) ◽  
pp. 4158-4163 ◽  
Author(s):  
Nelcy Thazar-Poulot ◽  
Martine Miquel ◽  
Isabelle Fobis-Loisy ◽  
Thierry Gaude
Keyword(s):  
Protein Trafficking ◽  
Protein Transport ◽  
Energy Resource ◽  
High Energy ◽  
Eukaryotic Cells ◽  
Oil Bodies ◽  
Energy Demands ◽  
Lipid Store ◽  
Lipid Stores

Lipid droplets/oil bodies (OBs) are lipid-storage organelles that play a crucial role as an energy resource in a variety of eukaryotic cells. Lipid stores are mobilized in the case of food deprivation or high energy demands—for example, during certain developmental processes in animals and plants. OB degradation is achieved by lipases that hydrolyze triacylglycerols (TAGs) into free fatty acids and glycerol. In the model plant Arabidopsis thaliana, Sugar-Dependent 1 (SDP1) was identified as the major TAG lipase involved in lipid reserve mobilization during seedling establishment. Although the enzymatic activity of SDP1 is associated with the membrane of OBs, its targeting to the OB surface remains uncharacterized. Here we demonstrate that the core retromer, a complex involved in protein trafficking, participates in OB biogenesis, lipid store degradation, and SDP1 localization to OBs. We also report an as-yet-undescribed mechanism for lipase transport in eukaryotic cells, with SDP1 being first localized to the peroxisome membrane at early stages of seedling growth and then possibly moving to the OB surface through peroxisome tubulations. Finally, we show that the timely transfer of SDP1 to the OB membrane requires a functional core retromer. In addition to revealing previously unidentified functions of the retromer complex in plant cells, our work provides unanticipated evidence for the role of peroxisome dynamics in interorganelle communication and protein transport.

scholarly journals Control of protein trafficking by reversible masking of transport signals

2016 ◽  
Vol 27 (8) ◽  
pp. 1310-1319 ◽  
Author(s):  
Omer Abraham ◽  
Karnit Gotliv ◽  
Anna Parnis ◽  
Gaelle Boncompain ◽  
Franck Perez ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Trafficking ◽  
Protein Transport ◽  
Protein Import ◽  
Binding Peptide ◽  
Protein Traffic ◽  
Alternative Approach ◽  
Targeting Signal ◽  
Regulated Trafficking ◽  
Streptavidin Binding

Systems that allow the control of protein traffic between subcellular compartments have been valuable in elucidating trafficking mechanisms. Most current approaches rely on ligand or light-controlled dimerization, which results in either retardation or enhancement of the transport of a reporter. We developed an alternative approach for trafficking regulation that we term “controlled unmasking of targeting elements” (CUTE). Regulated trafficking is achieved by reversible masking of the signal that directs the reporter to its target organelle, relying on the streptavidin–biotin system. The targeting signal is generated within or immediately after a 38–amino acid streptavidin-binding peptide (SBP) that is appended to the reporter. The binding of coexpressed streptavidin to SBP causes signal masking, whereas addition of biotin causes complex dissociation and triggers protein transport to the target organelle. We demonstrate the application of this approach to the control of nuclear and peroxisomal protein import and the generation of biotin-dependent trafficking through the endocytic and COPI systems. By simultaneous masking of COPI and endocytic signals, we were able to generate a synthetic pathway for efficient transport of a reporter from the plasma membrane to the endoplasmic reticulum.

scholarly journals Identification of a 25-kD protein from yeast cytosol that operates in a prefusion step of vesicular transport between compartments of the Golgi.

1990 ◽  
Vol 110 (4) ◽  
pp. 947-954 ◽  
Author(s):  
B W Wattenberg ◽  
R R Hiebsch ◽  
L W LeCureux ◽  
M P White
Keyword(s):  
Monoclonal Antibodies ◽  
Golgi Apparatus ◽  
Active Component ◽  
Protein Transport ◽  
Transport Activity ◽  
Yeast Protein ◽  
Fusion Event ◽  
Transport Vesicles ◽  
Target Membrane ◽  
Cytosolic Factors

We have identified a 25-kD cytosolic yeast protein that mediates a late, prefusion step in transport of proteins between compartments of the Golgi apparatus. Activity was followed using the previously described cell free assay for protein transport between Golgi compartments as modified to detect late acting cytosolic factors (Wattenberg, B. W., and J. E. Rothman. 1986. J. Biol. Chem. 263:2208-2213). In the reaction mediated by this protein, transport vesicles that have become attached to the target membrane during a preincubation are processed in preparation for fusion. The ultimate fusion event does not require the addition of cytosolic proteins (Balch, W. E., W. G. Dunphy, W. A. Braell, and J. E. Rothman. 1984. Cell. 39:525-536). Although isolated from yeast, this protein has activity when assayed with mammalian membranes. This protein has been enriched over 150-fold from yeast cytosol, albeit not to complete homogeneity. The identity of a 25-kD polypeptide as the active component was confirmed by raising monoclonal antibodies to it. These antibodies were found to specifically inhibit transport activity. Because this is a protein operating in prefusion, it has been abbreviated POP.

scholarly journals Lateral transport of Smoothened from the plasma membrane to the membrane of the cilium

2009 ◽  
Vol 187 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Ljiljana Milenkovic ◽  
Matthew P. Scott ◽  
Rajat Rohatgi
Keyword(s):  
Plasma Membrane ◽  
Protein Trafficking ◽  
Primary Cilia ◽  
Protein Transport ◽  
Transmembrane Protein ◽  
Signaling Proteins ◽  
Lateral Transport ◽  
Transport Pathway ◽  
Ciliary Membrane ◽  
Specific Proteins

The function of primary cilia depends critically on the localization of specific proteins in the ciliary membrane. A major challenge in the field is to understand protein trafficking to cilia. The Hedgehog (Hh) pathway protein Smoothened (Smo), a 7-pass transmembrane protein, moves to cilia when a ligand is received. Using microscopy-based pulse-chase analysis, we find that Smo moves through a lateral transport pathway from the plasma membrane to the ciliary membrane. Lateral movement, either via diffusion or active transport, is quite distinct from currently studied pathways of ciliary protein transport in mammals, which emphasize directed trafficking of Golgi-derived vesicles to the base of the cilium. We anticipate that this alternative route will be used by other signaling proteins that function at cilia. The path taken by Smo may allow novel strategies for modulation of Hh signaling in cancer and regeneration.

scholarly journals The role and mechanism of chaperones Calnexin/Calreticulin in which ALLN selectively rescues the trafficking defective of HERG-A561V mutation

2018 ◽  
Vol 38 (5) ◽  
Author(s):  
Ying Wang ◽  
Tingting Shen ◽  
Peiliang Fang ◽  
Junbo Zhou ◽  
Kenan Lou ◽  
...  
Keyword(s):  
Western Blot ◽  
Protein Trafficking ◽  
Protein Transport ◽  
Dominant Negative ◽  
Mutant Protein ◽  
Patch Clamp Technique ◽  
Long Qt ◽  
Truncated Protein ◽  
Maximal Peak

Long QT (LQT) type 2 (LQT2) is caused by HERG mutation. L539fs/47 encodes a truncated protein, and its mechanisms in HERG mutation are unknown. HERG mutation plasmids were overexpressed in HEK293T cells, respectively, followed by analyzing lysates with Western blot. Transfected HEK293T cells were treated with or without N-acetyl-l-leucyl-l-leucyl-l-norleucinal (ALLN) and Propranolol (Prop) at 24 or 48 h. HERG-WT, HERG-A561V, WT/A561V, HERG-L539fs/47, WT/L539fs/47, and Calnexin (CNX)/Calreticulin (CRT) protein expression and their interactions were detected by Western blot and immunoprecipitation. Each group with HERG currents (Ikr) were detected by Patch-clamp technique. Treated with ALLN, the expression of mature HERG protein and the CNX/CRT protein increased. The interaction of HERG-A561V and WT/A561V protein with the chaperone CNX/CRT increased significantly. The maximum peak currents and tail currents density increased by 70% and 73%, respectively, while maximal peak currents density (24%) and tail currents density (19%) were slight increased in WT-HERG cells. Treated with Prop, the expression and interaction of mature HERG and chaperones CNX/CRT had no difference in each group. The maximal currents and tail currents density were slight increased. CNX/CRT might play a crucial role in the trafficking-deficient process and degradation of HERG-A561V mutant protein, however they had no effect on L539fs/47 HERG due to protein transport deletion. ALLN can restore HERG-A561V mutant protein trafficking process and rescue the dominant negative suppression of WT-HERG.

scholarly journals Involvement of Long Chain Fatty Acid Elongation in the Trafficking of Secretory Vesicles in Yeast

1998 ◽  
Vol 143 (5) ◽  
pp. 1167-1182 ◽  
Author(s):  
Doris David ◽  
Sumathy Sundarababu ◽  
Jeffrey E. Gerst
Keyword(s):  
Protein Trafficking ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Lipid Synthesis ◽  
Carboxypeptidase Y ◽  
Secretory Vesicles ◽  
Recessive Mutations ◽  
General Protein ◽  
Yeast Mutants ◽  
Long Chain

Members of the synaptobrevin/VAMP family of v-SNAREs are thought to be essential for vesicle docking and exocytosis in both lower and higher eukaryotes. Here, we describe yeast mutants that appear to bypass the known v-SNARE requirement in secretion. Recessive mutations in either VBM1 or VBM2, which encode related ER-localized membrane proteins, allow yeast to grow normally and secrete in the absence of Snc v-SNAREs. These mutants show selective alterations in protein transport, resulting in the differential trafficking and secretion of certain protein cargo. Yet, processing of the vacuolar marker, carboxypeptidase Y, and the secreted protein, invertase, appear normal in these mutants indicating that general protein trafficking early in the pathway is unaffected. Interestingly, VBM1 and VBM2 are allelic to ELO3 and ELO2, two genes that have been shown recently to mediate the elongation of very long chain fatty acids and subsequent ceramide and inositol sphingolipid synthesis. Thus, the v-SNARE requirement in constitutive exocytosis is abrogated by mutations in early components of the secretory pathway that act at the level of lipid synthesis to affect the ability of secretory vesicles to sort and deliver protein cargo.

scholarly journals Vam7p, a SNAP-25-Like Molecule, and Vam3p, a Syntaxin Homolog, Function Together in Yeast Vacuolar Protein Trafficking

1998 ◽  
Vol 18 (9) ◽  
pp. 5308-5319 ◽  
Author(s):  
Trey K. Sato ◽  
Tamara Darsow ◽  
Scott D. Emr
Keyword(s):  
Protein Trafficking ◽  
Protein Transport ◽  
Coiled Coil ◽  
Snare Complex ◽  
Temperature Sensitive ◽  
Physical Interaction ◽  
Nonpermissive Temperature ◽  
Coiled Coil Domain ◽  
Px Domain ◽  
Vacuolar Protein

ABSTRACT A genetic screen to isolate gene products required for vacuolar morphogenesis in the yeast Saccharomyces cerevisiaeidentified VAM7, a gene which encodes a protein containing a predicted coiled-coil domain homologous to the coiled-coil domain of the neuronal t-SNARE, SNAP-25 (Y. Wada and Y. Anraku, J. Biol. Chem. 267:18671–18675, 1992; T. Weimbs, S. H. Low, S. J. Chapin, K. E. Mostov, P. Bucher, and K. Hofmann, Proc. Natl. Acad. Sci. USA 94:3046–3051, 1997). Analysis of a temperature-sensitive-for-function (tsf) allele ofVAM7 (vam7tsf ) demonstrated that the VAM7 gene product directly functions in vacuolar protein transport. vam7tsf mutant cells incubated at the nonpermissive temperature displayed rapid defects in the delivery of multiple proteins that traffic to the vacuole via distinct biosynthetic pathways. Examination ofvam7tsf cells at the nonpermissive temperature by electron microscopy revealed the accumulation of aberrant membranous compartments that may represent unfused transport intermediates. A fraction of Vam7p was localized to vacuolar membranes. Furthermore,VAM7 displayed genetic interactions with the vacuolar syntaxin homolog, VAM3. Consistent with the genetic results, Vam7p physically associated in a complex containing Vam3p, and this interaction was enhanced by inactivation of the yeast NSF (N-ethyl maleimide-sensitive factor) homolog, Sec18p. In addition to the coiled-coil domain, Vam7p also contains a putative NADPH oxidase p40phox (PX) domain. Changes in two conserved amino acids within this domain resulted in synthetic phenotypes when combined with the vam3tsf mutation, suggesting that the PX domain is required for Vam7p function. This study provides evidence for the functional and physical interaction between Vam7p and Vam3p at the vacuolar membrane, where they function as part of a t-SNARE complex required for the docking and/or fusion of multiple transport intermediates destined for the vacuole.

scholarly journals Differential Roles of Syntaxin 7 and Syntaxin 8 in Endosomal Trafficking

1999 ◽  
Vol 10 (11) ◽  
pp. 3891-3908 ◽  
Author(s):  
Rytis Prekeris ◽  
Bin Yang ◽  
Viola Oorschot ◽  
Judith Klumperman ◽  
Richard H. Scheller
Keyword(s):  
Membrane Fusion ◽  
Protein Trafficking ◽  
Molecular Mechanisms ◽  
Protein Transport ◽  
Growth Factor Receptor ◽  
Endosomal Trafficking ◽  
Attachment Protein ◽  
Early Endosomes ◽  
Protein Receptors ◽  
And Function

To understand molecular mechanisms that regulate the intricate and dynamic organization of the endosomal compartment, it is important to establish the morphology, molecular composition, and functions of the different organelles involved in endosomal trafficking. Syntaxins and vesicle-associated membrane protein (VAMP) families, also known as soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs), have been implicated in mediating membrane fusion and may play a role in determining the specificity of vesicular trafficking. Although several SNAREs, including VAMP3/cellubrevin, VAMP8/endobrevin, syntaxin 13, and syntaxin 7, have been localized to the endosomal membranes, their precise localization, biochemical interactions, and function remain unclear. Furthermore, little is known about SNAREs involved in lysosomal trafficking. So far, only one SNARE, VAMP7, has been localized to late endosomes (LEs), where it is proposed to mediate trafficking of epidermal growth factor receptor to LEs and lysosomes. Here we characterize the localization and function of two additional endosomal syntaxins, syntaxins 7 and 8, and propose that they mediate distinct steps of endosomal protein trafficking. Both syntaxins are found in SNARE complexes that are dissociated by α-soluble NSF attachment protein and NSF. Syntaxin 7 is mainly localized to vacuolar early endosomes (EEs) and may be involved in protein trafficking from the plasma membrane to the EE as well as in homotypic fusion of endocytic organelles. In contrast, syntaxin 8 is likely to function in clathrin-independent vesicular transport and membrane fusion events necessary for protein transport from EEs to LEs.

scholarly journals PTBP2-dependent alternative splicing regulates protein transport and mitochondria morphology in post-meiotic germ cells.

2018 ◽  
Author(s):  
Molly M Hannigan ◽  
Hisashi Fujioka ◽  
Adina Brett-Morris ◽  
Jason A Mears ◽  
Donny D Licatalosi
Keyword(s):  
Alternative Splicing ◽  
Germ Cells ◽  
Protein Trafficking ◽  
Rna Splicing ◽  
Protein Transport ◽  
Rna Binding ◽  
Binding Protein ◽  
Polypyrimidine Tract Binding Protein ◽  
Alternative Mrna Splicing ◽  
Genes Encoding

The RNA binding protein PTBP2 (polypyrimidine tract binding protein 2) is a key regulator of tissue-specific alternative RNA splicing. In the testis, PTBP2 is expressed in meiotic and post-meiotic germ cells (spermatocytes and spermatids, respectively). In these cells, PTBP2 is required for proper alternative mRNA splicing for over 200 genes, disproportionately affecting genes encoding proteins involved in protein trafficking via transport vesicles. In this study, we used electron microscopy to test the hypothesis that protein trafficking is impaired in the absence of PTBP2, and to further investigate why spermatogenesis abruptly halts in PTBP2-deficient spermatids. Ultrastructural analysis shows that protein trafficking in spermatids is aberrant in the absence of PTBP2. Unexpectedly, we also found that mitochondria morphology and number are significantly altered in PTBP2-deficient spermatids, consistent with increased mitochondria fission. Furthermore, we show that genes with key roles in mitochondria dynamics and function are post-transcriptionally regulated by PTBP2 and in different stages of spermatogenesis. Collectively, the data provide ultrastructural evidence that alternative splicing regulation by PTBP2 during spermatogenesis is critical for proper regulation of protein trafficking and mitochondria morphology.

scholarly journals Targeting endoplasmic reticulum protein transport: a novel strategy to kill malignant B cells and overcome fludarabine resistance in CLL

Blood ◽  
2006 ◽  
Vol 107 (1) ◽  
pp. 222-231 ◽  
Author(s):  
Jennifer S. Carew ◽  
Steffan T. Nawrocki ◽  
Yelena V. Krupnik ◽  
Kenneth Dunner ◽  
David J. McConkey ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
B Cells ◽  
Protein Trafficking ◽  
Protein Transport ◽  
Brefeldin A ◽  
Secretory Protein ◽  
Lymphocytic Leukemia ◽  
Mtdna Mutations ◽  
Golgi Protein ◽  
Induced Apoptosis

Abstract Previous studies showed that chronic lymphocytic leukemia (CLL) cells exhibit certain mitochondrial abnormalities including mtDNA mutations, increased superoxide generation, and aberrant mitochondrial biogenesis, which are associated with impaired apoptosis and reduced sensitivity to fludarabine. Here we report that CLL cells and multiple myeloma cells are highly sensitive to brefeldin A, an inhibitor of endoplasmic reticulum (ER) to Golgi protein transport currently being developed as a novel anticancer agent in a prodrug formulation. Of importance, brefeldin A effectively induced apoptosis in fludarabine-refractory CLL cells. Disruption of protein trafficking by brefeldin A caused the sequestration of the prosurvival factors APRIL and VEGF in the ER, leading to abnormal ER swelling and a decrease in VEGF secretion. Such ER stress and blockage of secretory protein traffic eventually resulted in Golgi collapse, activation of caspases, and cell death. Notably, the cellular sensitivity to this compound appeared to be independent of p53 status. Taken together, these findings suggest that malignant B cells may be highly dependent on ER-Golgi protein transport and that targeting this process may be a promising therapeutic strategy for B-cell malignancies, especially for those that respond poorly to conventional treatments.

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