scholarly journals Family-wide characterization of the DENN domain Rab GDP-GTP exchange factors

2010 ◽  
Vol 191 (2) ◽  
pp. 367-381 ◽  
Author(s):  
Shin-ichiro Yoshimura ◽  
Andreas Gerondopoulos ◽  
Andrea Linford ◽  
Daniel J. Rigden ◽  
Francis A. Barr
Keyword(s):  
Membrane Trafficking ◽  
Endocytic Pathway ◽  
Site Specific ◽  
Future Studies ◽  
Membrane Compartment ◽  
And Function ◽  
Apical Sorting ◽  
Golgi Network ◽  
And Control

A key requirement for Rab function in membrane trafficking is site-specific activation by GDP-GTP exchange factors (GEFs), but the majority of the 63 human Rabs have no known GEF. We have performed a systematic characterization of the 17 human DENN domain proteins and demonstrated that they are specific GEFs for 10 Rabs. DENND1A/1B localize to clathrin patches at the plasma membrane and activate Rab35 in an endocytic pathway trafficking Shiga toxin to the trans-Golgi network. DENND2 GEFs target to actin filaments and control Rab9-dependent trafficking of mannose-6-phosphate receptor to lysosomes. DENND4 GEFs target to a tubular membrane compartment adjacent to the Golgi, where they activate Rab10, which suggests a function in basolateral polarized sorting in epithelial cells that compliments the non-DENN GEF Sec2 acting on Rab8 in apical sorting. DENND1C, DENND3, DENND5A/5B, MTMR5/13, and MADD activate Rab13, Rab12, Rab39, Rab28, and Rab27A/27B, respectively. Together, these findings provide a basis for future studies on Rab regulation and function.

scholarly journals Reinterpretation of the localization of the ATP binding cassette transporter ABCG1 in insulin-secreting cells and insights regarding its trafficking and function

2018 ◽  
Author(s):  
Megan T. Harris ◽  
Syed Saad Hussain ◽  
Candice M. Inouye ◽  
Anna M. Castle ◽  
J. David Castle
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Pancreatic Beta Cells ◽  
Endocytic Pathway ◽  
Granule Formation ◽  
Oxysterol Binding Protein ◽  
Insulin Granules ◽  
Insulin Secreting Cells ◽  
And Function ◽  
Golgi Network

AbstractThe ABC transporter ABCG1 regulates intracellular cholesterol. We showed previously that ABCG1 deficiency inhibits insulin secretion by pancreatic beta cells and, based on its immunolocalization to insulin granules, proposed its essential role in forming cholesterol-enriched granule membranes. While we confirm elsewhere that ABCG1, alongside ABCA1 and oxysterol binding protein OSBP, supports insulin granule formation, the aim here is to update our localization and to provide added insight regarding ABCG1’s trafficking and sites of function. We show that stably expressed GFP-tagged ABCG1 closely mimics the distribution of endogenous ABCG1 in pancreatic INS1 cells and accumulates in the trans-Golgi network (TGN), endosomal recycling compartment (ERC) and on the cell surface but not on insulin granules, early or late endosomes. Notably, ABCG1 is short-lived, and proteasomal and lysosomal inhibitors both decrease its degradation. Following blockade of protein synthesis, GFP-ABCG1 first disappears from the ER and TGN and later from the ERC and plasma membrane. Beyond aiding granule formation, our findings raise the prospect that ABCG1 may act beyond the TGN to regulate activities involving the endocytic pathway, especially as the amount of transferrin receptor is increased in ABCGI-deficient cells. Thus, ABCG1 may function at multiple intracellular sites and the plasma membrane as a roving sensor and modulator of cholesterol distribution and membrane trafficking.

scholarly journals The PKD-Dependent Biogenesis of TGN-to-Plasma Membrane Transport Carriers

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1618
Author(s):  
Yuichi Wakana ◽  
Felix Campelo
Keyword(s):  
Cell Surface ◽  
Membrane Trafficking ◽  
Surface Protein ◽  
Membrane Contact Sites ◽  
Tissue Organization ◽  
Constitutive Secretion ◽  
Membrane Contact ◽  
Golgi Network ◽  
Organelle Membrane ◽  
And Control

Membrane trafficking is essential for processing and transport of proteins and lipids and to establish cell compartmentation and tissue organization. Cells respond to their needs and control the quantity and quality of protein secretion accordingly. In this review, we focus on a particular membrane trafficking route from the trans-Golgi network (TGN) to the cell surface: protein kinase D (PKD)-dependent pathway for constitutive secretion mediated by carriers of the TGN to the cell surface (CARTS). Recent findings highlight the importance of lipid signaling by organelle membrane contact sites (MCSs) in this pathway. Finally, we discuss our current understanding of multiple signaling pathways for membrane trafficking regulation mediated by PKD, G protein-coupled receptors (GPCRs), growth factors, metabolites, and mechanosensors.

scholarly journals Site-specific deacylation by ABHD17a controls BK channel splice variant activity

2020 ◽  
Vol 295 (49) ◽  
pp. 16487-16496 ◽  
Author(s):  
Heather McClafferty ◽  
Hamish Runciman ◽  
Michael J. Shipston
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Membrane Trafficking ◽  
Transmembrane Protein ◽  
Surface Expression ◽  
Bk Channels ◽  
Bk Channel ◽  
Site Specific ◽  
And Function ◽  
A Site

S-Acylation, the reversible post-translational lipid modification of proteins, is an important mechanism to control the properties and function of ion channels and other polytopic transmembrane proteins. However, although increasing evidence reveals the role of diverse acyl protein transferases (zDHHC) in controlling ion channel S-acylation, the acyl protein thioesterases that control ion channel deacylation are very poorly defined. Here we show that ABHD17a (α/β-hydrolase domain-containing protein 17a) deacylates the stress-regulated exon domain of large conductance voltage- and calcium-activated potassium (BK) channels inhibiting channel activity independently of effects on channel surface expression. Importantly, ABHD17a deacylates BK channels in a site-specific manner because it has no effect on the S-acylated S0–S1 domain conserved in all BK channels that controls membrane trafficking and is deacylated by the acyl protein thioesterase Lypla1. Thus, distinct S-acylated domains in the same polytopic transmembrane protein can be regulated by different acyl protein thioesterases revealing mechanisms for generating both specificity and diversity for these important enzymes to control the properties and functions of ion channels.

Characterization of Endocytic Pathways by Quantitative Fluorescence Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 1024-1025
Author(s):  
Frederick R. Maxfield ◽  
Richik N. Ghosh ◽  
William G. Mallet ◽  
Thwe Thwe Soe ◽  
Philip L. Leopold ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Surface ◽  
Light And Electron Microscopy ◽  
Endocytic Pathway ◽  
Early Endosomes ◽  
Pass Through ◽  
Golgi Network ◽  
Quantitative Fluorescence ◽  
Endocytic Pathways

We have used light and electron microscopy to analyze endocytic trafficking pathways. In one set of studies, we have used fluorescently labeled antibodies to trace an endocytic pathway from the cell surface to the trans- Golgi network (TGN). Cells were transfected with a construct consisting of the transmembrane and cytoplasmic domains of TGN38 and the extracellular domain of Tac. TGN38 is predominantly in the TGN, but a small fraction is found on the cell surface. We used FITC-labeled anti-Tac monoclonal IgG to analyze the pathway from the surface to the TGN. We compared the distribution of internalized Tac-TGN38 to internalized transferrin. We found that most Tac-TGN38 enters the same early endosomes as transferrin. Furthermore, most Tac-TGN38 returns to the cell surface from the endocytic recycling compartment (ERC) at the same rate as transferrin. However, on each pass through the cell approximately 18% of Tac-TGN is retained, and this Tac-TGN38 is delivered to the TGN.

scholarly journals Mechanism and Control of Meiotic DNA Double-Strand Break Formation in S. cerevisiae

2021 ◽  
Vol 9 ◽  
Author(s):  
Vikash Kumar Yadav ◽  
Corentin Claeys Bouuaert
Keyword(s):  
Strand Break ◽  
Current View ◽  
Dna Double Strand Breaks ◽  
Recombination Mechanism ◽  
Regulatory Pathways ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
And Function ◽  
And Control

Developmentally programmed formation of DNA double-strand breaks (DSBs) by Spo11 initiates a recombination mechanism that promotes synapsis and the subsequent segregation of homologous chromosomes during meiosis. Although DSBs are induced to high levels in meiosis, their formation and repair are tightly regulated to minimize potentially dangerous consequences for genomic integrity. In S. cerevisiae, nine proteins participate with Spo11 in DSB formation, but their molecular functions have been challenging to define. Here, we describe our current view of the mechanism of meiotic DSB formation based on recent advances in the characterization of the structure and function of DSB proteins and discuss regulatory pathways in the light of recent models.

Characterization of the cation-independent mannose 6-phosphate receptor-enriched prelysosomal compartment in NRK cells

1990 ◽  
Vol 95 (3) ◽  
pp. 441-461
Author(s):  
G. Griffiths ◽  
R. Matteoni ◽  
R. Back ◽  
B. Hoflack
Keyword(s):  
Acid Phosphatase ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Endocytic Pathway ◽  
Dimensional Structure ◽  
Surface Areas ◽  
Early Endosomes ◽  
Mannose 6 Phosphate ◽  
Golgi Network

The structure of a late endosomal compartment, which contains the bulk of the cation-independent mannose 6-phosphate receptor (MPR) in NRK cells, is documented using immunocytochemistry and cryo-sections, as well as conventional Epon sections. This compartment, which we refer to as the prelysosomal compartment (PLC), has a complex three-dimensional structure consisting of tubuloreticular domains in continuity with vesicular parts. The latter are characterized by a high density of internal membranes, which may be either tubular or sheet-like, that label extensively for the MPR. This structural organization was also maintained after fractionation in sucrose gradients. The amount of MPR immunolabelling was then quantitated with respect to the membrane surface areas of the four compartments where it is found: namely, the plasma membrane, early endosomes, the trans Golgi network and the PLC. The results showed that in NRK cells 90% of the labelling for the receptor was found in the PLC, with the rest distributed over the other three compartments. Cytochemical studies indicated that the PLC is the first structure along the endocytic pathway that gives a significant reaction for acid phosphatase. However, the PLC is clearly distinct from the MPR-negative lysosomes, which are also acid phosphatase-positive, since the two organelles could be physically separated from each other after fractionation on Percoll gradients.

GGA proteins: new players in the sorting game

2001 ◽  
Vol 114 (19) ◽  
pp. 3413-3418 ◽  
Author(s):  
Annette L. Boman
Keyword(s):  
Membrane Trafficking ◽  
Sequence Homology ◽  
Mammalian Cells ◽  
Gene Knockout ◽  
Protein Domains ◽  
Vesicle Formation ◽  
Trans Golgi Network ◽  
And Function ◽  
Golgi Network ◽  
Cargo Sorting

The GGA proteins are a novel family of proteins that were discovered nearly simultaneously by several labs studying very different aspects of membrane trafficking. Since then, several studies have described the GGA proteins and their functions in yeast and mammalian cells. Four protein domains are present in all GGA proteins, as defined by sequence homology and function. These different domains interact directly with ARF proteins, cargo and clathrin. Alteration of the levels of GGA proteins by gene knockout or overexpression affects specific trafficking events between the trans-Golgi network and endosomes. These data suggest that GGAs function as ARF-dependent, monomeric clathrin adaptors to facilitate cargo sorting and vesicle formation at the trans-Golgi network.

scholarly journals The power, pitfalls and potential of the nanodisc system for NMR-based studies

2016 ◽  
Vol 397 (12) ◽  
pp. 1335-1354 ◽  
Author(s):  
Aldino Viegas ◽  
Thibault Viennet ◽  
Manuel Etzkorn
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Membrane Proteins ◽  
Lipid Bilayer ◽  
Structure And Function ◽  
Fundamental Importance ◽  
Future Studies ◽  
And Function ◽  
Unique Potential

Abstract The choice of a suitable membrane mimicking environment is of fundamental importance for the characterization of structure and function of membrane proteins. In this respect, usage of the lipid bilayer nanodisc technology provides a unique potential for nuclear magnetic resonance (NMR)-based studies. This review summarizes the recent advances in this field, focusing on (i) the strengths of the system, (ii) the bottlenecks that may be faced, and (iii) promising capabilities that may be explored in future studies.

Early endocytic Rabs: functional prediction to functional characterization.

2005 ◽  
Vol 72 ◽  
pp. 99-108 ◽  
Author(s):  
Jeremy C Simpson ◽  
Arwyn T Jones
Keyword(s):  
Membrane Trafficking ◽  
Functional Characterization ◽  
Specific Interaction ◽  
Small Gtpases ◽  
Endocytic Pathway ◽  
Functional Prediction ◽  
Final Destination ◽  
Similarities And Differences ◽  
And Function ◽  
Endocytic Pathways

Endocytic pathways are highly dynamic gateways for molecules to enter cells. Functionality and specificity is in part controlled by a number of small GTPases called Rabs. In defined cellular locations, Rabs mediate multiple functions in membrane trafficking via their specific interaction with organelle membranes and a host of affector and effector molecules. On endocytic pathways, Rabs have been shown to control the formation of vesicles on the plasma membrane and the downstream delivery of internalized molecules to a number of cellular locations. As numerous Rabs are located to endocytic pathways, an internalized molecule may traverse a number of Rab specific substations or subdomains en route to its final destination. Rabs 5, 21 and 22 have all been localized to the early endocytic pathway and have been shown to share a number of characteristics to merit their segregation into a single functional endocytic group. In this review, we compare experiments that describe similarities and differences in endosome morphology and function that is mediated by their expression in cells.

scholarly journals Annexin XIIIb Associates with Lipid Microdomains to Function in Apical Delivery

1998 ◽  
Vol 142 (6) ◽  
pp. 1413-1427 ◽  
Author(s):  
Frank Lafont ◽  
Sandra Lecat ◽  
Paul Verkade ◽  
Kai Simons
Keyword(s):  
Membrane Trafficking ◽  
Physiological Function ◽  
Apical Cell ◽  
The Other ◽  
In Vitro Assays ◽  
Kidney Cells ◽  
Vesicular Carriers ◽  
Apical Sorting ◽  
Golgi Network

A member of the annexin XIII sub-family, annexin XIIIb, has been implicated in the apical exocytosis of epithelial kidney cells. Annexins are phospholipid-binding proteins that have been suggested to be involved in membrane trafficking events although their actual physiological function remains open. Unlike the other annexins, annexin XIIIs are myristoylated. Here, we show by immunoelectron microscopy that annexin XIIIb is localized to the trans-Golgi network (TGN), vesicular carriers and the apical cell surface. Polarized apical sorting involves clustering of apical proteins into dynamic sphingolipid-cholesterol rafts. We now provide evidence for the raft association of annexin XIIIb. Using in vitro assays and either myristoylated or unmyristoylated recombinant annexin XIIIb, we demonstrate that annexin XIIIb in its native myristoylated form stimulates specifically apical transport whereas the unmyristoylated form inhibits this route. Moreover, we show that formation of apical carriers from the TGN is inhibited by an anti-annexin XIIIb antibody whereas it is stimulated by myristoylated recombinant annexin XIIIb. These results suggest that annexin XIIIb directly participates in apical delivery.

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