Autophagy gene ATG7 regulates albumin transcytosis in renal tubule epithelial cells

Author(s):  
Yushi Uchida ◽  
Kumiko Torisu ◽  
Kenji Ueki ◽  
Kazuhiko Tsuruya ◽  
Toshiaki Nakano ◽  
...  

Receptor-mediated albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. Autophagy is an evolutionarily conserved degradation pathway and its role in intracellular trafficking through interaction with the endocytic pathway has recently been highlighted. Here, we determined whether autophagy regulates albumin transcytosis in PTECs and suppresses albumin-induced cytotoxicity using human proximal tubule (HK-2) cells. Neonatal Fc-receptor (FcRn), a receptor for albumin transcytosis, partially co-localized with autophagosomes. Recycling of FcRn was attenuated and FcRn accumulated in autophagy related 7 (ATG7) knockdown HK-2 cells. Co-localization of FcRn with RAB7-positive late endosomes and RAB11-positive recycling endosomes was reduced in ATG7 knockdown cells, resulting in decreased recycling of FcRn to the plasma membrane. In ATG7 knockdown cells, albumin transcytosis was significantly reduced and intracellular albumin accumulation was increased. Finally, release of KIM-1, a marker of tubule injury, from ATG7 knockdown cells was increased in response to excess albumin. In conclusion, suppression of autophagy in tubules impairs FcRn transport, thereby inhibiting albumin transcytosis. The resulting accumulation of albumin induces cytotoxicity in tubules.

1995 ◽  
Vol 129 (1) ◽  
pp. 55-64 ◽  
Author(s):  
A Hémar ◽  
A Subtil ◽  
M Lieb ◽  
E Morelon ◽  
R Hellio ◽  
...  

Members of the cytokine receptor family are composed of several noncovalently linked chains with sequence and structure homologies in their extracellular domain. Receptor subfamily members share at least one component: thus the receptors for interleukin (IL) 2 and IL15 have common beta and gamma chains, while those for IL2, 4, 7, and 9 have a common gamma chain. The intracellular pathway followed by IL2 receptors after ligand binding and endocytosis was analyzed by immunofluorescence and confocal microscopy in a human T lymphocytic cell line. Surprisingly, the alpha, beta, and gamma chains had different intracellular localizations after being endocytosed together. The alpha chain was always in transferrin-positive compartments (early/recycling endosomes), both at early and late internalization times, but was never detected in rab7-positive compartments (late endosomes). On the other hand, at late internalization times, the beta and gamma chains were excluded from transferrin-positive organelles and did not colocalize with alpha. Furthermore, beta could be found in rab7-positive vesicles. These differences suggest that the alpha chain recycles to the plasma membrane, while the beta and gamma chains are sorted towards the degradation pathway. The half-lives of these three chains on the cell surface also reflect their different intracellular fates after endocytosis. The beta and gamma chains are very short-lived polypeptides since their half-life on the surface is only approximately 1 h, whereas alpha is a much more stable surface protein. This shows for the first time that components of a multimeric receptor can be sorted separately along the endocytic pathway.


1994 ◽  
Vol 107 (5) ◽  
pp. 1289-1295 ◽  
Author(s):  
V. Duprez ◽  
M. Smoljanovic ◽  
M. Lieb ◽  
A. Dautry-Varsat

The T lymphocyte growth factor interleukin 2 binds to surface high-affinity receptors and is rapidly internalized and degraded in acidic organelles. The alpha and beta chains of high-affinity interleukin 2 receptors are internalized together with interleukin 2. To identify the intracellular pathway followed by interleukin 2, we have compared the subcellular distribution of interleukin 2, transferrin and a fluid-phase marker, horseradish peroxidase, in the human T cell line IARC 301.5. Transferrin was used as a marker of early and recycling endosomes, and horseradish peroxidase to probe for the whole endocytic pathway. Fractionation of intracellular organelles on a discontinuous sucrose gradient showed that internalized interleukin 2 is initially mostly found in compartments with similar densities to transferrin, e.g. early and recycling endosomes. The kinetics of entry and exit of interleukin 2 from such organelles was much slower than that of transferrin. Later on, interleukin 2 is predominantly found in dense lysosome-containing fractions. Very little, if any, interleukin 2 was found in fractions corresponding to late endosomes containing horseradish peroxidase. These results suggest that, after endocytosis, interleukin 2 enters early or recycling endosomes before it reaches dense lysosomes.


1997 ◽  
Vol 110 (17) ◽  
pp. 2079-2087 ◽  
Author(s):  
L.J. Robinson ◽  
F. Aniento ◽  
J. Gruenberg

Protein transport between early and late endosomes is a major membrane trafficking pathway in the cell followed by many proteins, including all down-regulated receptors. Yet, little is known at the molecular level about the mechanisms regulating membrane interactions in the endocytic pathway beyond early endosomes. In this study, we have used an in vitro transport assay to study the biochemical properties of endosome docking/fusion events. Our data demonstrate that N-ethylmaleimide (NEM) sensitive factor (NSF) and its soluble associated proteins (SNAPs) are required for transport from early to late endosomes, as well as at all other steps of endosomal membrane transport. We also find that these proteins are enriched on endosomal membranes. In addition, our studies suggest that besides NSF/SNAPs, another NEM-sensitive component may also be involved in docking/fusion at this late stage of the pathway. Finally, we find that, in contrast to Golgi membranes, NSF association to both early and late endosomal membranes occurs via an ATP-independent mechanism, indicating that the binding properties of endosomal and biosynthetic NSF are different. Our data thus show that NSF/SNAPs, perhaps together with another NEM-sensitive factor, are part of the basic molecular machinery which controls docking/fusion events during transport from early to late endosomes, along the lysosomal degradation pathway.


2004 ◽  
Vol 15 (11) ◽  
pp. 4798-4806 ◽  
Author(s):  
Rajalaxmi Natarajan ◽  
Adam D. Linstedt

Toxins can invade cells by using a direct endosome-to-Golgi endocytic pathway that bypasses late endosomes/prelysosomes. This is also a route used by endogenous proteins, including GPP130, which is an integral membrane protein retrieved via the bypass pathway from endosomes to its steady-state location in the cis-Golgi. An RNA interference-based test revealed that GPP130 was required for efficient exit of Shiga toxin B-fragment from endosomes en route to the Golgi apparatus. Furthermore, two proteins whose Golgi targeting depends on endosome-to-Golgi retrieval in the bypass pathway accumulated in early/recycling endosomes in the absence of GPP130. GPP130 activity seemed specific to bypass pathway trafficking because the targeting of other tested proteins, including those retrieved to the Golgi via the more conventional late endosome route, was unaltered. Thus, a distally cycling Golgi protein mediates exit from endosomes and thereby underlies Shiga toxin invasion and retrieval-based targeting of other cycling Golgi proteins.


1998 ◽  
Vol 143 (4) ◽  
pp. 973-990 ◽  
Author(s):  
Frédéric Mallard ◽  
Claude Antony ◽  
Danièle Tenza ◽  
Jean Salamero ◽  
Bruno Goud ◽  
...  

Shiga toxin and other toxins of this family can escape the endocytic pathway and reach the Golgi apparatus. To synchronize endosome to Golgi transport, Shiga toxin B-fragment was internalized into HeLa cells at low temperatures. Under these conditions, the protein partitioned away from markers destined for the late endocytic pathway and colocalized extensively with cointernalized transferrin. Upon subsequent incubation at 37°C, ultrastructural studies on cryosections failed to detect B-fragment–specific label in multivesicular or multilamellar late endosomes, suggesting that the protein bypassed the late endocytic pathway on its way to the Golgi apparatus. This hypothesis was further supported by the rapid kinetics of B-fragment transport, as determined by quantitative confocal microscopy on living cells and by B-fragment sulfation analysis, and by the observation that actin- depolymerizing and pH-neutralizing drugs that modulate vesicular transport in the late endocytic pathway had no effect on B-fragment accumulation in the Golgi apparatus. B-fragment sorting at the level of early/recycling endosomes seemed to involve vesicular coats, since brefeldin A treatment led to B-fragment accumulation in transferrin receptor–containing membrane tubules, and since B-fragment colocalized with adaptor protein type 1 clathrin coat components on early/recycling endosomes. Thus, we hypothesize that Shiga toxin B-fragment is transported directly from early/recycling endosomes to the Golgi apparatus. This pathway may also be used by cellular proteins, as deduced from our finding that TGN38 colocalized with the B-fragment on its transport from the plasma membrane to the TGN.


2012 ◽  
Vol 80 (10) ◽  
pp. 3410-3416 ◽  
Author(s):  
Masahiro Nagahama ◽  
Mariko Umezaki ◽  
Ryo Tashiro ◽  
Masataka Oda ◽  
Keiko Kobayashi ◽  
...  

ABSTRACTClostridium perfringensiota-toxin is composed of an enzymatic component (Ia) and a binding component (Ib). Ib binds to a cell surface receptor, undergoes oligomerization in lipid rafts, and binds Ia. The resulting complex is then endocytosed. Here, we show the intracellular trafficking of iota-toxin. After the binding of the Ib monomer with cells at 4°C, oligomers of Ib formed at 37°C and later disappeared. Immunofluorescence staining of Ib revealed that the internalized Ib was transported to early endosomes. Some Ib was returned to the plasma membrane through recycling endosomes, whereas the rest was transported to late endosomes and lysosomes for degradation. Degraded Ib was delivered to the plasma membrane by an increase in the intracellular Ca2+concentration caused by Ib. Bafilomycin A1, an endosomal acidification inhibitor, caused the accumulation of Ib in endosomes, and both nocodazole and colchicine, microtubule-disrupting agents, restricted Ib's movement in the cytosol. These results indicated that an internalized Ia and Ib complex was delivered to early endosomes and that subsequent delivery of Ia to the cytoplasm occurs mainly in early endosomes. Ib was either sent back to the plasma membranes through recycling endosomes or transported to late endosomes and lysosomes for degradation. Degraded Ib was transported to plasma membranes.


2001 ◽  
Vol 152 (6) ◽  
pp. 1183-1196 ◽  
Author(s):  
Atsushi Suzuki ◽  
Tomoyuki Yamanaka ◽  
Tomonori Hirose ◽  
Naoyuki Manabe ◽  
Keiko Mizuno ◽  
...  

We have previously shown that during early Caenorhabditis elegans embryogenesis PKC-3, a C. elegans atypical PKC (aPKC), plays critical roles in the establishment of cell polarity required for subsequent asymmetric cleavage by interacting with PAR-3 [Tabuse, Y., Y. Izumi, F. Piano, K.J. Kemphues, J. Miwa, and S. Ohno. 1998. Development (Camb.). 125:3607–3614]. Together with the fact that aPKC and a mammalian PAR-3 homologue, aPKC-specific interacting protein (ASIP), colocalize at the tight junctions of polarized epithelial cells (Izumi, Y., H. Hirose, Y. Tamai, S.-I. Hirai, Y. Nagashima, T. Fujimoto, Y. Tabuse, K.J. Kemphues, and S. Ohno. 1998. J. Cell Biol. 143:95–106), this suggests a ubiquitous role for aPKC in establishing cell polarity in multicellular organisms. Here, we show that the overexpression of a dominant-negative mutant of aPKC (aPKCkn) in MDCK II cells causes mislocalization of ASIP/PAR-3. Immunocytochemical analyses, as well as measurements of paracellular diffusion of ions or nonionic solutes, demonstrate that the biogenesis of the tight junction structure itself is severely affected in aPKCkn-expressing cells. Furthermore, these cells show increased interdomain diffusion of fluorescent lipid and disruption of the polarized distribution of Na+,K+-ATPase, suggesting that epithelial cell surface polarity is severely impaired in these cells. On the other hand, we also found that aPKC associates not only with ASIP/PAR-3, but also with a mammalian homologue of C. elegans PAR-6 (mPAR-6), and thereby mediates the formation of an aPKC-ASIP/PAR-3–PAR-6 ternary complex that localizes to the apical junctional region of MDCK cells. These results indicate that aPKC is involved in the evolutionarily conserved PAR protein complex, and plays critical roles in the development of the junctional structures and apico-basal polarization of mammalian epithelial cells.


Sign in / Sign up

Export Citation Format

Share Document