scholarly journals The Palmitoyltransferase of the Cation-dependent Mannose 6-Phosphate Receptor Cycles between the Plasma Membrane and Endosomes

2004 ◽  
Vol 15 (6) ◽  
pp. 2617-2626 ◽  
Author(s):  
Jacqueline Stöckli ◽  
Jack Rohrer
Keyword(s):  
Plasma Membrane ◽  
Protein Trafficking ◽  
Specific Protein ◽  
Cysteine Residue ◽  
Endocytic Pathway ◽  
Cell Homogenate ◽  
Mannose 6 Phosphate ◽  
Golgi Network

The cation-dependent mannose 6-phosphate receptor (CD-MPR) mediates the transport of lysosomal enzymes from the trans-Golgi network to endosomes. Evasion of lysosomal degradation of the CD-MPR requires reversible palmitoylation of a cysteine residue in its cytoplasmic tail. Because palmitoylation is reversible and essential for correct trafficking, it presents a potential regulatory mechanism for the sorting signals within the cytoplasmic domain of the CD-MPR. Characterization of the palmitoylation performing an in vitro palmitoylation assay by using purified full-length CD-MPR revealed that palmitoylation of the CD-MPR occurs enzymatically by a membrane-bound palmitoyltransferase. In addition, analysis of the localization revealed that the palmitoyltransferase cycles between endosomes and the plasma membrane. This was identified by testing fractions from HeLa cell homogenate separated on a density gradient in the in vitro palmitoylation assay and further confirmed by in vivo labeling experiments by using different treatments to block specific protein trafficking steps within the cell. We identified a novel palmitoyltransferase activity in the endocytic pathway responsible for palmitoylation of the CD-MPR. The localization of the palmitoyltransferase not only fulfills the requirement of our hypothesis to be a regulator of the intracellular trafficking of the CD-MPR but also may affect the sorting/activity of other receptors cycling through endosomes.

scholarly journals Specific Translocation of Protein Kinase Cα to the Plasma Membrane Requires Both Ca2+ and PIP2 Recognition by Its C2 Domain

2006 ◽  
Vol 17 (1) ◽  
pp. 56-66 ◽  
Author(s):  
John H. Evans ◽  
Diana Murray ◽  
Christina C. Leslie ◽  
Joseph J. Falke
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Membrane Binding ◽  
Membrane Lipid ◽  
C2 Domain ◽  
Plasma Membrane Lipid ◽  
Protein Kinase Cα ◽  
Golgi Network

The C2 domain of protein kinase Cα (PKCα) controls the translocation of this kinase from the cytoplasm to the plasma membrane during cytoplasmic Ca2+ signals. The present study uses intracellular coimaging of fluorescent fusion proteins and an in vitro FRET membrane-binding assay to further investigate the nature of this translocation. We find that Ca2+-activated PKCα and its isolated C2 domain localize exclusively to the plasma membrane in vivo and that a plasma membrane lipid, phosphatidylinositol-4,5-bisphosphate (PIP2), dramatically enhances the Ca2+-triggered binding of the C2 domain to membranes in vitro. Similarly, a hybrid construct substituting the PKCα Ca2+-binding loops (CBLs) and PIP2 binding site (β-strands 3–4) into a different C2 domain exhibits native Ca2+-triggered targeting to plasma membrane and recognizes PIP2. Conversely, a hybrid containing the CBLs but lacking the PIP2 site translocates primarily to trans-Golgi network (TGN) and fails to recognize PIP2. Similarly, PKCα C2 domains possessing mutations in the PIP2 site target primarily to TGN and fail to recognize PIP2. Overall, these findings demonstrate that the CBLs are essential for Ca2+-triggered membrane binding but are not sufficient for specific plasma membrane targeting. Instead, targeting specificity is provided by basic residues on β-strands 3–4, which bind to plasma membrane PIP2.

The role of the Lowe syndrome protein OCRL in the endocytic pathway

2015 ◽  
Vol 396 (12) ◽  
pp. 1293-1300 ◽  
Author(s):  
Shruti Sharma ◽  
Agnieszka Skowronek ◽  
Kai Sven Erdmann
Keyword(s):  
Genetic Disorders ◽  
Endocytic Pathway ◽  
Lowe Syndrome ◽  
Coated Pits ◽  
Golgi Network ◽  
Endocytic Compartments ◽  
Syndrome Protein

Abstract Mutations of the inositol-5-phosphatase OCRL cause Lowe syndrome and Dent-II disease. Both are rare genetic disorders characterized by renal defects. Lowe syndrome is furthermore characterized by defects of the eye (congenital cataracts) and nervous system (mental disabilities, hypotonia). OCRL has been localised to various endocytic compartments suggesting impairments in the endocytic pathway as possible disease mechanism. Recent evidence strongly supports this view and shows essential roles of OCRL at clathrin coated pits, transport of cargo from endosomes to the trans-Golgi network as well as recycling of receptors from endosomes to the plasma membrane. In particular in vitro and in vivo evidence demonstrates an important role of OCRL in recycling of megalin, a multi-ligand receptor crucial for reabsorption of nutrients in the proximal tubulus, a process severely impaired in Lowe syndrome patients. Thus defects in the endocytic pathway are likely to significantly contribute to the kidney phenotype in Lowe syndrome and Dent-II disease.

scholarly journals The Variable Domain of a Plant Calcium-dependent Protein Kinase (CDPK) Confers Subcellular Localization and Substrate Recognition for NADPH Oxidase

2013 ◽  
Vol 288 (20) ◽  
pp. 14332-14340 ◽  
Author(s):  
Shuta Asai ◽  
Tatsushi Ichikawa ◽  
Hironari Nomura ◽  
Michie Kobayashi ◽  
Yusuke Kamiyoshihara ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Nadph Oxidase ◽  
Subcellular Localization ◽  
Expression System ◽  
Calcium Dependent ◽  
Dependent Protein ◽  
Golgi Network ◽  
Respiratory Burst Oxidase

Calcium-dependent protein kinases (CDPKs) are Ca2+ sensors that regulate diverse biological processes in plants and apicomplexans. However, how CDPKs discriminate specific substrates in vivo is still largely unknown. Previously, we found that a potato StCDPK5 is dominantly localized to the plasma membrane and activates the plasma membrane NADPH oxidase (RBOH; for respiratory burst oxidase homolog) StRBOHB by direct phosphorylation of the N-terminal region. Here, we report the contribution of the StCDPK5 N-terminal variable (V) domain to activation of StRBOHB in vivo using heterologous expression system in Nicotiana benthamiana. Mutations of N-terminal myristoylation and palmitoylation sites in the V domain eliminated the predominantly plasma membrane localization and the capacity of StCDPK5 to activate StRBOHB in vivo. A tomato SlCDPK2, which also contains myristoylation and palmitoylation sites in its N terminus, phosphorylated StRBOHB in vitro but not in vivo. Functional domains responsible for activation and phosphorylation of StRBOHB were identified by swapping regions for each domain between StCDPK5 and SlCDPK2. The substitution of the V domain of StCDPK5 with that of SlCDPK2 abolished the activation and phosphorylation abilities of StRBOHB in vivo and relocalized the chimeric CDPK to the trans-Golgi network, as observed for SlCDPK2. Conversely, SlCDPK2 substituted with the V domain of StCDPK5 localized to the plasma membrane and activated StRBOHB. These results suggest that the V domains confer substrate specificity in vivo by dictating proper subcellular localization of CDPKs.

Interaction of amphiphysins with AP-1 clathrin adaptors at the membrane

2013 ◽  
Vol 450 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Sonja Huser ◽  
Gregor Suri ◽  
Pascal Crottet ◽  
Martin Spiess
Keyword(s):  
Plasma Membrane ◽  
Brefeldin A ◽  
Adaptor Protein ◽  
Trans Golgi Network ◽  
Src Homology 3 ◽  
Amphiphysin 1 ◽  
Src Homology ◽  
Golgi Network

The assembly of clathrin/AP (adaptor protein)-1-coated vesicles on the trans-Golgi network and endosomes is much less studied than that of clathrin/AP-2 vesicles at the plasma membrane for endocytosis. In vitro, the association of AP-1 with protein-free liposomes had been shown to require phosphoinositides, Arf1 (ADP-ribosylation factor 1)–GTP and additional cytosolic factor(s). We have purified an active fraction from brain cytosol and found it to contain amphiphysin 1 and 2 and endophilin A1, three proteins known to be involved in the formation of AP-2/clathrin coats at the plasma membrane. Assays with bacterially expressed and purified proteins showed that AP-1 stabilization on liposomes depends on amphiphysin 2 or the amphiphysin 1/2 heterodimer. Activity is independent of the SH3 (Src homology 3) domain, but requires interaction of the WDLW motif with γ-adaptin. Endogenous amphiphysin in neurons and transfected protein in cell lines co-localize perinuclearly with AP-1 at the trans-Golgi network. This localization depends on interaction of clathrin and the adaptor sequence in the amphiphysins and is sensitive to brefeldin A, which inhibits Arf1-dependent AP-1 recruitment. Interaction between AP-1 and amphiphysin 1/2 in vivo was demonstrated by co-immunoprecipitation after cross-linking. These results suggest an involvement of amphiphysins not only with AP-2 at the plasma membrane, but also in AP-1/clathrin coat formation at the trans-Golgi network.

scholarly journals Mammalian GGAs act together to sort mannose 6-phosphate receptors

2003 ◽  
Vol 163 (4) ◽  
pp. 755-766 ◽  
Author(s):  
Pradipta Ghosh ◽  
Janice Griffith ◽  
Hans J. Geuze ◽  
Stuart Kornfeld
Keyword(s):  
Protein Trafficking ◽  
Immunogold Electron Microscopy ◽  
Partial Redistribution ◽  
Golgi Membranes ◽  
Vitro Binding ◽  
Mannose 6 Phosphate ◽  
Golgi Network ◽  
Adp Ribosylation Factor ◽  
Chemical Cross Linking

The GGAs (Golgi-localized, γ ear–containing, ADP ribosylation factor–binding proteins) are multidomain proteins implicated in protein trafficking between the Golgi and endosomes. We examined whether the three mammalian GGAs act independently or together to mediate their functions. Using cryo-immunogold electron microscopy, the three GGAs were shown to colocalize within coated buds and vesicles at the trans-Golgi network (TGN) of HeLa cells. In vitro binding experiments revealed multidomain interactions between the GGAs, and chemical cross-linking experiments demonstrated that GGAs 1 and 2 form a complex on Golgi membranes. RNA interference of each GGA resulted in decreased levels of the other GGAs and their redistribution from the TGN to cytosol. This was associated with impaired incorporation of the cation-independent mannose 6-phosphate receptor into clathrin-coated vesicles at the TGN, partial redistribution of the receptor to endosomes, and missorting of cathepsin D. The morphology of the TGN was also altered. These findings indicate that the three mammalian GGAs cooperate to sort cargo and are required for maintenance of TGN structure.

Specific Labeling of Protein Domains with Antibody Fragments

1981 ◽  
Vol 39 ◽  
pp. 416-417
Author(s):  
U. Aebi ◽  
L.E. Buhle ◽  
W.E. Fowler
Keyword(s):  
Image Processing ◽  
Specific Protein ◽  
Antibody Fragments ◽  
Supramolecular Organization ◽  
Two Dimensional ◽  
Ordered Structures ◽  
Virus Capsids ◽  
Processing Techniques

Many important supramolecular structures such as filaments, microtubules, virus capsids and certain membrane proteins and bacterial cell walls exist as ordered polymers or two-dimensional crystalline arrays in vivo. In several instances it has been possible to induce soluble proteins to form ordered polymers or two-dimensional crystalline arrays in vitro. In both cases a combination of electron microscopy of negatively stained specimens with analog or digital image processing techniques has proven extremely useful for elucidating the molecular and supramolecular organization of the constituent proteins. However from the reconstructed stain exclusion patterns it is often difficult to identify distinct stain excluding regions with specific protein subunits. To this end it has been demonstrated that in some cases this ambiguity can be resolved by a combination of stoichiometric labeling of the ordered structures with subunit-specific antibody fragments (e.g. Fab) and image processing of the electron micrographs recorded from labeled and unlabeled structures.

scholarly journals RNF141 interacts with KRAS to promote colorectal cancer progression

Oncogene ◽  
2021 ◽  
Author(s):  
Jiuna Zhang ◽  
Xiaoyu Jiang ◽  
Jie Yin ◽  
Shiying Dou ◽  
Xiaoli Xie ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Plasma Membrane ◽  
Tumor Growth ◽  
Cancer Progression ◽  
Critical Role ◽  
Ring Finger ◽  
Immunohistochemical Analysis ◽  
Bimolecular Fluorescence Complementation

AbstractRING finger proteins (RNFs) play a critical role in cancer initiation and progression. RNF141 is a member of RNFs family; however, its clinical significance, roles, and mechanism in colorectal cancer (CRC) remain poorly understood. Here, we examined the expression of RNF141 in 64 pairs of CRC and adjacent normal tissues by real-time PCR, Western blot, and immunohistochemical analysis. We found that there was more expression of RNF141 in CRC tissue compared with its adjacent normal tissue and high RNF141 expression associated with T stage. In vivo and in vitro functional experiments were conducted and revealed the oncogenic role of RNF141 in CRC. RNF141 knockdown suppressed proliferation, arrested the cell cycle in the G1 phase, inhibited migration, invasion and HUVEC tube formation but promoted apoptosis, whereas RNF141 overexpression exerted the opposite effects in CRC cells. The subcutaneous xenograft models showed that RNF141 knockdown reduced tumor growth, but its overexpression promoted tumor growth. Mechanistically, liquid chromatography-tandem mass spectrometry indicated RNF141 interacted with KRAS, which was confirmed by Co-immunoprecipitation, Immunofluorescence assay. Further analysis with bimolecular fluorescence complementation (BiFC) and Glutathione-S-transferase (GST) pull-down assays showed that RNF141 could directly bind to KRAS. Importantly, the upregulation of RNF141 increased GTP-bound KRAS, but its knockdown resulted in a reduction accordingly. Next, we demonstrated that RNF141 induced KRAS activation via increasing its enrichment on the plasma membrane not altering total KRAS expression, which was facilitated by the interaction with LYPLA1. Moreover, KRAS silencing partially abolished the effect of RNF141 on cell proliferation and apoptosis. In addition, our findings presented that RNF141 functioned as an oncogene by upregulating KRAS activity in a manner of promoting KRAS enrichment on the plasma membrane in CRC.

scholarly journals Norepinephrine Protects against Methamphetamine Toxicity through β2-Adrenergic Receptors Promoting LC3 Compartmentalization

2021 ◽  
Vol 22 (13) ◽  
pp. 7232
Author(s):  
Gloria Lazzeri ◽  
Carla L. Busceti ◽  
Francesca Biagioni ◽  
Cinzia Fabrizi ◽  
Gabriele Morucci ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Light Chain ◽  
Adrenergic Receptors ◽  
Cell Damage ◽  
Protective Effects ◽  
Autophagy Flux ◽  
Brain Areas ◽  
Indirect Consequence

Norepinephrine (NE) neurons and extracellular NE exert some protective effects against a variety of insults, including methamphetamine (Meth)-induced cell damage. The intimate mechanism of protection remains difficult to be analyzed in vivo. In fact, this may occur directly on target neurons or as the indirect consequence of NE-induced alterations in the activity of trans-synaptic loops. Therefore, to elude neuronal networks, which may contribute to these effects in vivo, the present study investigates whether NE still protects when directly applied to Meth-treated PC12 cells. Meth was selected based on its detrimental effects along various specific brain areas. The study shows that NE directly protects in vitro against Meth-induced cell damage. The present study indicates that such an effect fully depends on the activation of plasma membrane β2-adrenergic receptors (ARs). Evidence indicates that β2-ARs activation restores autophagy, which is impaired by Meth administration. This occurs via restoration of the autophagy flux and, as assessed by ultrastructural morphometry, by preventing the dissipation of microtubule-associated protein 1 light chain 3 (LC3) from autophagy vacuoles to the cytosol, which is produced instead during Meth toxicity. These findings may have an impact in a variety of degenerative conditions characterized by NE deficiency along with autophagy impairment.

scholarly journals Synaptotagmin IV is necessary for the maturation of secretory granules in PC12 cells

2006 ◽  
Vol 173 (2) ◽  
pp. 241-251 ◽  
Author(s):  
Malika Ahras ◽  
Grant P. Otto ◽  
Sharon A. Tooze
Keyword(s):  
Pc12 Cells ◽  
Secretory Granules ◽  
Granule Formation ◽  
Synaptotagmin Iv ◽  
Prohormone Convertase 2 ◽  
Granule Maturation ◽  
Golgi Network ◽  
Interfering Rna

In neuroendocrine PC12 cells, immature secretory granules (ISGs) mature through homotypic fusion and membrane remodeling. We present evidence that the ISG-localized synaptotagmin IV (Syt IV) is involved in ISG maturation. Using an in vitro homotypic fusion assay, we show that the cytoplasmic domain (CD) of Syt IV, but not of Syt I, VII, or IX, inhibits ISG homotypic fusion. Moreover, Syt IV CD binds specifically to ISGs and not to mature secretory granules (MSGs), and Syt IV binds to syntaxin 6, a SNARE protein that is involved in ISG maturation. ISG homotypic fusion was inhibited in vivo by small interfering RNA–mediated depletion of Syt IV. Furthermore, the Syt IV CD, as well as Syt IV depletion, reduces secretogranin II (SgII) processing by prohormone convertase 2 (PC2). PC2 is found mostly in the proform, suggesting that activation of PC2 is also inhibited. Granule formation, and the sorting of SgII and PC2 from the trans-Golgi network into ISGs and MSGs, however, is not affected. We conclude that Syt IV is an essential component for secretory granule maturation.

scholarly journals Interactions between RNA polymerase and the core recognition element are a determinant of transcription start site selection

2016 ◽  
Vol 113 (21) ◽  
pp. E2899-E2905 ◽  
Author(s):  
Irina O. Vvedenskaya ◽  
Hanif Vahedian-Movahed ◽  
Yuanchao Zhang ◽  
Deanne M. Taylor ◽  
Richard H. Ebright ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Transcription Start Site ◽  
Transcription Initiation ◽  
Specific Protein ◽  
Start Site ◽  
Transcription Start ◽  
Transcription Bubble ◽  
Recognition Element

During transcription initiation, RNA polymerase (RNAP) holoenzyme unwinds ∼13 bp of promoter DNA, forming an RNAP-promoter open complex (RPo) containing a single-stranded transcription bubble, and selects a template-strand nucleotide to serve as the transcription start site (TSS). In RPo, RNAP core enzyme makes sequence-specific protein–DNA interactions with the downstream part of the nontemplate strand of the transcription bubble (“core recognition element,” CRE). Here, we investigated whether sequence-specific RNAP–CRE interactions affect TSS selection. To do this, we used two next-generation sequencing-based approaches to compare the TSS profile of WT RNAP to that of an RNAP derivative defective in sequence-specific RNAP–CRE interactions. First, using massively systematic transcript end readout, MASTER, we assessed effects of RNAP–CRE interactions on TSS selection in vitro and in vivo for a library of 47 (∼16,000) consensus promoters containing different TSS region sequences, and we observed that the TSS profile of the RNAP derivative defective in RNAP–CRE interactions differed from that of WT RNAP, in a manner that correlated with the presence of consensus CRE sequences in the TSS region. Second, using 5′ merodiploid native-elongating-transcript sequencing, 5′ mNET-seq, we assessed effects of RNAP–CRE interactions at natural promoters in Escherichia coli, and we identified 39 promoters at which RNAP–CRE interactions determine TSS selection. Our findings establish RNAP–CRE interactions are a functional determinant of TSS selection. We propose that RNAP–CRE interactions modulate the position of the downstream end of the transcription bubble in RPo, and thereby modulate TSS selection, which involves transcription bubble expansion or transcription bubble contraction (scrunching or antiscrunching).

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