| 1. |
- Abu-Siniyeh, Ahmed, et al.
(författare)
-
The aPKC/Par3/Par6 Polarity Complex and Membrane Order Are Functionally Interdependent in Epithelia During Vertebrate Organogenesis
- 2016
-
Ingår i: Traffic. - : Wiley. - 1398-9219 .- 1600-0854. ; 17:1, s. 66-79
-
Tidskriftsartikel (refereegranskat)abstract
- The differential distribution of lipids between apical and basolateral membranes is necessary for many epithelial cell functions, but how this characteristic membrane organization is integrated within the polarity network during ductal organ development is poorly understood. Here we quantified membrane order in the gut, kidney and liver ductal epithelia in zebrafish larvae at 3-11 days post fertilization (dpf) with Laurdan 2-photon microscopy. We then applied a combination of Laurdan imaging, antisense knock-down and analysis of polarity markers to understand the relationship between membrane order and apical-basal polarity. We found a reciprocal relationship between membrane order and the cell polarity network. Reducing membrane condensation by exogenously added oxysterol or depletion of cholesterol reduced apical targeting of the polarity protein, aPKC. Conversely, using morpholino knock down in zebrafish, we found that membrane order was dependent upon the Crb3 and Par3 polarity protein expression in ductal epithelia. Hence our data suggest that the biophysical property of membrane lipid packing is a regulatory element in apical basal polarity.
|
|
| 2. |
- Echbarthi, Meriem, et al.
(författare)
-
Distinct Trafficking of Cell Surface and Endosomal TIM-1 to the Immune Synapse
- 2015
-
Ingår i: Traffic : the International Journal of Intracellular Transport. - : Wiley. - 1398-9219 .- 1600-0854. ; 16:11, s. 1193-1207
-
Tidskriftsartikel (refereegranskat)abstract
- The T cell costimulatory molecule TIM-1 (T cell/transmembrane, mucin and immunoglobulin domain protein 1) sorts mainly to endosomes in lymphoid cells. At difference from the cell surface protein, endosomal TIM-1 translocates to the immune synapse (IS), where it can contribute to antigen-dependent T cell costimulation. TIM-1 ligands increase the amount of cell surface protein, preventing its traffic to the IS. The bipolar sorting of TIM-1 observed during IS formation is determined by differences in its subcellular location, and probably modulates antigen-driven immune responses. The T-cell/transmembrane, mucin and immunoglobulin domain protein 1 (TIM-1) is a phosphatidlyserine (PtdSer) receptor and a T-cell costimulatory molecule linked to the development of atopic diseases. TIM-1 locates preferentially in intracellular compartments. Here we show that in human and mouse lymphoid cells, TIM-1 localizes in different types of endosomes and that its domain structure is important for protein sorting to intracellular vesicles. The BALB/c mouse TIM-1 protein, which has a longer mucin domain, is sorted more efficiently to endosomes than the shorter C57BL/6 variant. High affinity ligands such as PtdSer increase the amount of cell surface TIM-1; the protein also polarizes toward cell contacts with apoptotic cells. The large pool of intracellular TIM-1 translocates to the immune synapse (IS) with the CD3-TCR (T-cell receptor) complex and colocalizes to the central supramolecular activation cluster (cSMAC). In contrast, cell surface TIM-1 does not traffic to the IS, but is located away from it. The bipolar TIM-1 sorting observed during IS formation is determined by differences in its subcellular location, and might modulate antigen-driven immune responses. © 2015 John Wiley & Sons A/S.
|
|
| 3. |
- Karim, Mahmoud Abdul, et al.
(författare)
-
Distinct features of multivesicular body-lysosome fusion revealed by a new cell-free content-mixing assay
- 2018
-
Ingår i: Traffic. - : City Net Scientific Research Center Ltd. Belgrade, Serbia. - 1398-9219 .- 1600-0854. ; 19:2, s. 138-149
-
Tidskriftsartikel (refereegranskat)abstract
- When marked for degradation, surface receptor and transporter proteins are internalized and delivered to endosomes where they are packaged into intralumenal vesicles (ILVs). Many rounds of ILV formation create multivesicular bodies (MVBs) that fuse with lysosomes exposing ILVs to hydrolases for catabolism. Despite being critical for protein degradation, the molecular underpinnings of MVB-lysosome fusion remain unclear, although machinery underlying other lysosome fusion events is implicated. But how then is specificity conferred? And how is MVB maturation and fusion coordinated for efficient protein degradation? To address these questions, we developed a cell-free MVB-lysosome fusion assay using Saccharomyces cerevisiae as a model. After confirming that the Rab7 ortholog Ypt7 and the multisubunit tethering complex HOPS (homotypic fusion and vacuole protein sorting complex) are required, we found that the Qa-SNARE Pep12 distinguishes this event from homotypic lysosome fusion. Mutations that impair MVB maturation block fusion by preventing Ypt7 activation, confirming that a Rab-cascade mechanism harmonizes MVB maturation with lysosome fusion.
|
|
| 4. |
- Omar-Hmeadi, Muhmmad, et al.
(författare)
-
PtdIns(4,5)P2 is not required for secretory granule docking
- 2018
-
Ingår i: Traffic. - : Wiley. - 1398-9219 .- 1600-0854. ; 19:6, s. 436-445
-
Tidskriftsartikel (refereegranskat)abstract
- Phosphoinositides (PtdIns) play important roles in exocytosis and are thought to regulate secretory granule docking by co-clustering with the SNARE protein syntaxin to form a docking receptor in the plasma membrane. Here we tested this idea by high-resolution total internal reflection imaging of EGFP-labeled PtdIns markers or syntaxin-1 at secretory granule release sites in live insulin-secreting cells. In intact cells, PtdIns markers distributed evenly across the plasma membrane with no preference for granule docking sites. In contrast, syntaxin-1 was found clustered in the plasma membrane, mostly beneath docked granules. We also observed rapid accumulation of syntaxin-1 at sites where granules arrived to dock. Acute depletion of plasma membrane phosphatidylinositol (4,5) bisphosphate (PtdIns(4,5)P-2) by recruitment of a 5-phosphatase strongly inhibited Ca2+-dependent exocytosis, but had no effect on docked granules or the distribution and clustering of syntaxin-1. Cell permeabilization by -toxin or formaldehyde-fixation caused PtdIns marker to slowly cluster, in part near docked granules. In summary, our data indicate that PtdIns(4,5)P-2 accelerates granule priming, but challenge a role of PtdIns in secretory granule docking or clustering of syntaxin-1 at the release site.
|
|
| 5. |
- Ring, Andreas, et al.
(författare)
-
Ssy1 functions at the plasma membrane as a receptor of extracellular amino acids independent of plasma membrane‐endoplasmic reticulum junctions
- 2019
-
Ingår i: Traffic. - : Wiley. - 1398-9219 .- 1600-0854. ; 20:10, s. 775-784
-
Tidskriftsartikel (refereegranskat)abstract
- Evidence from multiple laboratories have implicated Ssy1, a non‐transporting amino acid permease, as the receptor component of the yeast plasma membrane (PM)‐localized SPS (Ssy1‐Ptr3‐Ssy5)‐sensor. Upon binding external amino acids, Ssy1 is thought to initiate signaling events leading to the induction of amino acid permease gene expression. In striking contrast, Kralt et al. 2015 (Traffic 16:135‐147) have questioned the role of Ssy1 in amino acid sensing and reported that Ssy1 is a component of the endoplasmic reticulum (ER), where it reportedly participates in the formation of ER‐PM junctions. Here, we have re‐examined the intracellular location of Ssy1 and tested the role of ER‐PM junctions in SPS sensor signaling. We show that the C‐terminal of Ssy1 carries a functional ER‐exit motif required for proper localization of Ssy1 to the PM. Furthermore, ER‐PM junctions are dispensable for PM‐localization and function of Ssy1; Ssy1 localizes to the PM in a Δtether strain lacking ER‐PM junctions (ist2Δ scs2Δ scs22Δ tcb1Δ tcb2Δ tcb3Δ), and this strain retains the ability to initiate signals induced by extracellular amino acids. The data demonstrate that Ssy1 functions as the primary amino acid receptor and that it carries out this function at the PM.
|
|
| 6. |
|
|
| 7. |
- Zamponi, Nahuel, et al.
(författare)
-
Endoplasmic reticulum is the sorting core facility in the Golgi-lacking protozoan Giardia lamblia
- 2017
-
Ingår i: Traffic. - : Wiley. - 1398-9219 .- 1600-0854. ; 18:9, s. 604-621
-
Tidskriftsartikel (refereegranskat)abstract
- Our understanding of protein and lipid trafficking in eukaryotic cells has been challenged by the finding of different forms of compartmentalization and cargo processing in protozoan parasites. Here, we show that, in the absence of a Golgi compartment in Giardia, proteins destined for secretion are directly sorted and packaged at specialized ER regions enriched in COPII coatomer complexes and ceramide. We also demonstrated that ER-resident proteins are retained at the ER by the action of a KDEL receptor, which, in contrast to other eukaryotic KDEL receptors, showed no interorganellar dynamic but instead acts specifically at the limit of the ER membrane. Our study suggests that the ER-exit sites and the perinuclear ER-membranes are capable of performing protein-sorting functions. In our view, the description presented here suggests that Giardia adaptation represents an extreme example of reductive evolution without loss of function.
|
|
| 8. |
|
|
| 9. |
- Lindquist, Emelie, et al.
(författare)
-
Vesicles Are Persistent Features of Different Plastids
- 2016
-
Ingår i: Traffic. - : Wiley. - 1398-9219. ; 17:10, s. 1125-1138
-
Tidskriftsartikel (refereegranskat)abstract
- Peripheral vesicles in plastids have been observed repeatedly, primarily in proplastids and developing chloroplasts, in which they are suggested to function in thylakoid biogenesis. Previous observations of vesicles in mature chloroplasts have mainly concerned low temperature pretreated plants occasionally treated with inhibitors blocking vesicle fusion. Here, we show that such vesicle-like structures occur not only in chloroplasts and proplastids, but also in etioplasts, etio-chloroplasts, leucoplasts, chromoplasts and even transforming desiccoplasts without any specific pretreatment. Observations are made both in C3 and C4 species, in different cell types (meristematic, epidermis, mesophyll, bundle sheath and secretory cells) and different organs (roots, stems, leaves, floral parts and fruits). Until recently not much focus has been given to the idea that vesicle transport in chloroplasts could be mediated by proteins, but recent data suggest that the vesicle system of chloroplasts has similarities with the cytosolic coat protein complex II system. All current data taken together support the idea of an ongoing, active and protein-mediated vesicle transport not only in chloroplasts but also in other plastids, obviously occurring regardless of chemical modifications, temperature and plastid developmental stage. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
|
|
