101
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Nielsen R, Christensen EI. Proteinuria and events beyond the slit. Pediatr Nephrol 2010; 25:813-22. [PMID: 20049615 DOI: 10.1007/s00467-009-1381-9] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 10/27/2009] [Accepted: 10/27/2009] [Indexed: 11/30/2022]
Abstract
The origin of proteinuria is found in either the glomerular filtration device or the proximal tubular reabsorption machinery. During equilibrium, small amounts of predominantly low molecular weight proteins are filtered and reabsorbed by the receptor complex megalin/cubilin/amnionless. This results in a protein-free filtrate passing further down the tubule. During glomerular damage, the reabsorption machinery in the proximal tubule is challenged due to elevated amounts of proteins passing the glomerular filtration slits. Even though it is considered to be a high-capacity system, several conditions result in proteinuria, thus exposing the cells in the rest of the nephron to a protein-rich environment. The impact on cells in the more distal part of the nephron is uncertain, but studies support an involvement in fibrosis development. Protein accumulation in lysosomes of the proximal tubule, due to increased protein internalization, is thought to mediate inflammation and fibrosis, eventually leading to renal failure. In contrast, low molecular weight proteinuria develops when the endocytic machinery is malfunctioning either by direct or indirect causes such as in Imerslund-Gräsbeck syndrome (IGS) or Dent's disease, respectively. This review discusses the origin of proteinuria and describes the structural fundament for protein reabsorption in the proximal tubule as well as conditions resulting in low molecular weight proteinuria.
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Affiliation(s)
- Rikke Nielsen
- Department of Anatomy, Section of Cell Biology, Aarhus University, Building 1234, Aarhus C, Denmark
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102
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Rodriguez-Gabin AG, Ortiz E, Demoliner K, Si Q, Almazan G, Larocca JN. Interaction of Rab31 and OCRL-1 in oligodendrocytes: its role in transport of mannose 6-phosphate receptors. J Neurosci Res 2010; 88:589-604. [PMID: 19795375 DOI: 10.1002/jnr.22236] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Rab31, a protein that we cloned from an oligodendrocyte cDNA library, is required for transport of mannose 6-phosphate receptors (MPRs) from the trans-Golgi network (TGN) to endosomes and for Golgi/TGN organization. Here we extend the knowledge of the mechanism of action of Rab31 by demonstrating its interaction with OCRL-1, a phosphatidylinositol 4,5-diphosphate 5-phosphatase (PI(4,5)P(2) 5-phosphatase) that regulates the levels of PI(4,5)P(2) and PI(4)P, molecules involved in transport and Golgi/TGN organization. We show that Rab31 interacts with OCRL-1 in a yeast two-hybrid system, GST-Rab31 pull-down experiments, and coimmunoprecipitation of OCRL-1 using oligodendrocyte culture lysates. Rab31 and OCRL-1 colocalize in the TGN, post-TGN carriers, and endosomes. Cation-dependent MPR (CD-MPR) is sorted to OCRL-1-containing carriers, but CD63 and vesicular stomatitis virus G (VSVG) are not. siRNA-mediated depletion of endogenous Rab31 causes collapse of the TGN apparatus and markedly decreases the levels of OCRL-1 in the TGN and endosomes. Our observations indicate that the role of Rab31 in the Golgi/TGN structure and transport of MPRs depends on its capability to recruit OCRL-1 to domains of the TGN where the formation of carriers occurs. The importance of our observations is highlighted by the fact that mutation of OCRL-1 causes demyelination in humans.
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Affiliation(s)
- A G Rodriguez-Gabin
- Department of Neurology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461, USA
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103
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Multiple host proteins that function in phosphatidylinositol-4-phosphate metabolism are recruited to the chlamydial inclusion. Infect Immun 2010; 78:1990-2007. [PMID: 20231409 DOI: 10.1128/iai.01340-09] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chlamydiae replicate within a nonacidified vacuole, termed an inclusion. As obligate intracellular bacteria, chlamydiae actively modify their vacuole to exploit host signaling and trafficking pathways. Recently, we demonstrated that several Rab GTPases are actively targeted to the inclusion. To define the biological roles of inclusion localized Rab GTPases, we have begun to identify inclusion-localized Rab effectors. Here we demonstrate that oculocerebrorenal syndrome of Lowe protein 1 (OCRL1), a Golgi complex-localized phosphatidylinositol (PI)-5-phosphatase that binds to multiple Rab GTPases, localizes to chlamydial inclusions. By examining the intracellular localization of green fluorescent protein (GFP) fusion proteins that bind to unique phosphoinositide species, we also demonstrate that phosphatidylinositol-4-phosphate (PI4P), the product of OCRL1, is present at the inclusion membrane. Furthermore, two additional host proteins, Arf1, which together with PI4P mediates the recruitment of PI4P-binding proteins to the Golgi complex, and PI4KII alpha, a major producer of Golgi complex-localized PI4P, also localize to chlamydial inclusions. Depletion of OCRL1, Arf1, or PI4KII alpha by small interfering RNA (siRNA) decreases inclusion formation and the production of infectious progeny. Infectivity is further decreased in cells simultaneously depleted for all three host proteins, suggesting partially overlapping functions in infected cells. Collectively, these data demonstrate that Chlamydia species create a unique replication-competent vacuolar environment by modulating both the Rab GTPase and the PI composition of the chlamydial inclusion.
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104
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Two closely related endocytic proteins that share a common OCRL-binding motif with APPL1. Proc Natl Acad Sci U S A 2010; 107:3511-6. [PMID: 20133602 DOI: 10.1073/pnas.0914658107] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutations of the inositol 5' phosphatase oculocerebrorenal syndrome of Lowe (OCRL) give rise to the congenital X-linked disorders oculocerebrorenal syndrome of Lowe and Dent disease, two conditions giving rise to abnormal kidney proximal tubule reabsorption, and additional nervous system and ocular defects in the case of Lowe syndrome. Here, we identify two closely related endocytic proteins, Ses1 and Ses2, which interact with the ASH-RhoGAP-like (ASPM-SPD-2-Hydin homology and Rho-GTPase Activating Domain-like) domain of OCRL. The interaction is mediated by a short amino acid motif similar to that used by the rab-5 effector APPL1 (Adaptor Protein containing pleckstrin homology [PH] domain, PTB domain and Leucine zipper motif 1) APPL1 for OCRL binding. Ses binding is mutually exclusive with APPL1 binding, and is disrupted by the same missense mutations in the ASH-RhoGAP-like domain that also disrupt APPL1 binding. Like APPL1, Ses1 and -2 are localized on endosomes but reside on different endosomal subpopulations. These findings define a consensus motif (which we have called a phenylalanine and histidine [F&H] motif) for OCRL binding and are consistent with a scenario in which Lowe syndrome and Dent disease result from perturbations at multiple sites within the endocytic pathway.
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105
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Jovic M, Sharma M, Rahajeng J, Caplan S. The early endosome: a busy sorting station for proteins at the crossroads. Histol Histopathol 2010; 25:99-112. [PMID: 19924646 DOI: 10.14670/hh-25.99] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endocytosis marks the entry of internalized receptors into the complex network of endocytic trafficking pathways. Endocytic vesicles are rapidly targeted to a distinct membrane-bound endocytic organelle referred to as the early endosome. Despite the existence of numerous internalization routes, early endosomes (EE) serve as a focal point of the endocytic pathway. Sorting events initiated at this compartment determine the subsequent fate of internalized proteins and lipids, destining them either for recycling to the plasma membrane, degradation in lysosomes or delivery to the trans-Golgi network. Sorting of endocytic cargo to the latter compartments is accomplished through the formation of distinct microdomains within early endosomes, through the coordinate recruitment and assembly of the sorting machinery. An elaborate network of interactions between endocytic regulatory proteins ensures synchronized sorting of cargo to microdomains followed by morphological changes at the early endosomal membranes. Consequently, the cargo targeted either for recycling back to the plasma membrane, or for retrograde transport to the trans-Golgi network, localizes to newly-formed tubular membranes. With a high ratio of membrane surface to lumenal volume, these tubules effectively concentrate the recycling cargo, ensuring efficient transport out of the EE. Conversely, receptors sorted for degradation cluster at the flat clathrin lattices involved in invaginations of the limiting membrane, associating with newly formed intralumenal vesicles. In this review we will discuss the characteristics of early endosomes, their role in the regulation of endocytic transport, and their aberrant function in a variety of diseases.
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Affiliation(s)
- Marko Jovic
- Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5870, USA
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106
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Cui S, Guerriero CJ, Szalinski CM, Kinlough CL, Hughey RP, Weisz OA. OCRL1 function in renal epithelial membrane traffic. Am J Physiol Renal Physiol 2009; 298:F335-45. [PMID: 19940034 DOI: 10.1152/ajprenal.00453.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The X-linked disorder Lowe syndrome arises from mutations in OCRL1, a lipid phosphatase that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP(2)). Most patients with Lowe syndrome develop proteinuria very early in life. PIP(2) dynamics are known to modulate numerous steps in membrane trafficking, and it has been proposed that OCRL1 activity regulates the biogenesis or trafficking of the multiligand receptor megalin. To examine this possibility, we investigated the effects of siRNA-mediated OCRL1 knockdown on biosynthetic and postendocytic membrane traffic in canine and human renal epithelial cells. Cells depleted of OCRL1 did not have significantly elevated levels of cellular PIP(2) but displayed an increase in actin comets, as previously observed in cultured cells derived from Lowe patients. Using assays to independently quantitate the endocytic trafficking of megalin and of megalin ligands, we could observe no defect in the trafficking or function of megalin upon OCRL1 knockdown. Moreover, apical delivery of a newly synthesized marker protein was unaffected. OCRL1 knockdown did result in a significant increase in secretion of the lysosomal hydrolase cathepsin D, consistent with a role for OCRL1 in membrane trafficking between the trans-Golgi network and endosomes. Together, our studies suggest that OCRL1 does not directly modulate endocytosis or postendocytic membrane traffic and that the renal manifestations observed in Lowe syndrome patients are downstream consequences of the loss of OCRL1 function.
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Affiliation(s)
- Shanshan Cui
- Renal Electrolyte Division, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15261, USA
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107
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Botelho RJ. Changing phosphoinositides "on the fly": how trafficking vesicles avoid an identity crisis. Bioessays 2009; 31:1127-36. [PMID: 19708025 DOI: 10.1002/bies.200900060] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Joining an antagonistic phosphoinositide (PtdInsP) kinase and phosphatase into a single protein complex may regulate rapid and local PtdInsP changes. This may be important for processes such as membrane fission that require a specific PtdInsP and that are innately local and rapid. Such a complex could couple vesicle formation, with erasing of the identity of the donor organelle from the vesicle prior to its fusion with target organelles, thus preventing organelle identity intermixing. Coordinating signals are postulated to switch the relative activities of the kinase and phosphatase in a spatio-temporal manner that matches membrane fission events. The discovery of two such complexes supports this hypothesis. One regulates the interconversion of phosphatidylinositol and PtdIns(3)P by joining the Vps34 PtdIns 3-kinase and the myotubularin 3-phosphatases. The other regulates the interconversion between PtdIns(3)P and PtdIns(3,5)P(2) through the Fab1/PIKfyve kinase and the Fig4/mFig4 phosphatase. These lipids are essential components of the endosomal identity code.
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Affiliation(s)
- Roberto J Botelho
- Department of Chemistry and Biology, Ryerson University, ON, Canada.
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108
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Regulation of Golgi function via phosphoinositide lipids. Semin Cell Dev Biol 2009; 20:793-800. [PMID: 19508852 DOI: 10.1016/j.semcdb.2009.03.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 03/24/2009] [Accepted: 03/25/2009] [Indexed: 12/22/2022]
Abstract
Phosphoinositides play important roles in Golgi traffic and structural integrity. Specific lipid kinases and phosphatases associate with the Golgi complex and regulate the multiplicity of trafficking routes from this organelle. Work in different model systems showed that the basic elements that regulate lipid signaling at the Golgi are conserved from yeast to humans. Many of the enzymes involved in Golgi phosphoinositide metabolism are essential for viability or cause severe human disease when malfunctioning. Phosphoinositide effectors at the Golgi control both non-vesicular transfer of lipids and sorting of secretory and membrane proteins. In addition, Golgi phosphoinositides were recently implicated in the metabolic and cell growth-dependent regulation of the secretory pathway.
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109
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Abstract
Abnormalities in the central nervous system and renal function are seen together in a variety of congenital syndromes. This Review examines the clinical presentation and the genetic basis of several such syndromes. The X-linked oculocerebrorenal syndrome of Lowe is characterized by developmental delay, blindness, renal tubular dysfunction, and progressive renal failure. This syndrome results from mutations in the OCRL gene, which encodes a phosphatase involved in endosomal trafficking. Mutations in OCRL also occur in Dent disease, which has a milder disease phenotype than Lowe syndrome. Patients with Joubert syndrome have cerebellar ataxia, pigmentary retinopathy, and nephronophthisis. Joubert syndrome is a genetically heterogeneous condition associated with mutations in at least five genes that encode ciliary proteins. Bardet-Biedl syndrome is a clinically variable condition associated with learning disabilities, progressive visual loss, obesity, polydactyly, hypogonadism, and cystic and fibrotic renal changes that can lead to renal failure. Most of the 12 genes mutated in Bardet-Biedl syndrome are also involved in ciliary function, as are the genes implicated in other 'ciliopathies' with similar phenotypes, including Meckel syndrome.
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Affiliation(s)
- Scott J Schurman
- Department of Pediatrics, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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110
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Popoff V, Mardones GA, Bai SK, Chambon V, Tenza D, Burgos PV, Shi A, Benaroch P, Urbé S, Lamaze C, Grant BD, Raposo G, Johannes L. Analysis of articulation between clathrin and retromer in retrograde sorting on early endosomes. Traffic 2009; 10:1868-80. [PMID: 19874558 DOI: 10.1111/j.1600-0854.2009.00993.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Clathrin and retromer have key functions for retrograde trafficking between early endosomes and the trans-Golgi network (TGN). Previous studies on Shiga toxin suggested that these two coat complexes operate in a sequential manner. Here, we show that the curvature recognition subunit component sorting nexin 1 (SNX1) of retromer interacts with receptor-mediated endocytosis-8 (RME-8) protein, and that RME-8 and SNX1 colocalize on early endosomes together with a model cargo of the retrograde route, the receptor-binding B-subunit of Shiga toxin (STxB). RME-8 has previously been found to bind to the clathrin uncoating adenosine triphosphatase (ATPase) Hsc70, and we now report that depletion of RME-8 or Hsc70 affects retrograde trafficking at the early endosomes-TGN interface of STxB and the cation-independent mannose 6-phosphate receptor, an endogenous retrograde cargo protein. We also provide evidence that retromer interacts with the clathrin-binding protein hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) not only via SNX1, as previously published (Chin Raynor MC, Wei X, Chen HQ, Li L. Hrs interacts with sorting nexin 1 and regulates degradation of epidermal growth factor receptor. J Biol Chem 2001;276:7069-7078), but also via the core complex component Vps35. Hrs codistributes at the ultrastructural level with STxB on early endosomes, and interfering with Hrs function using antibodies or mild overexpression inhibits retrograde transport. Our combined data suggest a model according to which the functions in retrograde sorting on early endosomes of SNX1/retromer and clathrin are articulated by RME-8, and possibly also by Hrs.
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Affiliation(s)
- Vincent Popoff
- Institut Curie - Centre de Recherche, Traffic, Signaling and Delivery Laboratory, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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111
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Tosetto E, Addis M, Caridi G, Meloni C, Emma F, Vergine G, Stringini G, Papalia T, Barbano G, Ghiggeri GM, Ruggeri L, Miglietti N, D Angelo A, Melis MA, Anglani F. Locus heterogeneity of Dent's disease: OCRL1 and TMEM27 genes in patients with no CLCN5 mutations. Pediatr Nephrol 2009; 24:1967-73. [PMID: 19582483 DOI: 10.1007/s00467-009-1228-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 05/05/2009] [Accepted: 05/07/2009] [Indexed: 10/20/2022]
Abstract
Dent's disease is an X-linked renal tubulopathy caused by mutations mainly affecting the CLCN5 gene. Defects in the OCRL1 gene, which is usually mutated in patients with Lowe syndrome, have recently been shown to lead to a Dent-like phenotype, called Dent's disease 2. About 25% of Dent's disease patients do not carry CLCN5/OCRL1 mutations. The CLCN4 and SLC9A6 genes have been investigated, but no mutations have been identified. The recent discovery of a novel mediator of renal amino acid transport, collectrin (the TMEM27 gene), may provide new insight on the pathogenesis of Dent's disease. We studied 31 patients showing a phenotype resembling Dent's disease but lacking any CLCN5 mutations by direct sequencing of the OCRL1 and TMEM27 genes. Five novel mutations, L88X, P161HfsX167, F270S, D506N and E720D, in the OCRL1 gene, which have not previously been reported in patients with Dent's or Lowe disease, were identified among 11 patients with the classical Dent's disease phenotype. No TMEM27 gene mutations were discovered among 26 patients, 20 of whom had an incomplete Dent's disease phenotype. Our findings confirm that OCRL1 is involved in the functional defects characteristic of Dent's disease and suggest that patients carrying missense mutations in exons where many Lowe mutations are mapped may represent a phenotypic variant of Lowe syndrome.
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Affiliation(s)
- Enrica Tosetto
- Division of Nephrology, Department of Medical and Surgical Sciences, University of Padua, 35128 Padova, Italy
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112
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Koharudin LMI, Furey W, Liu H, Liu YJ, Gronenborn AM. The phox domain of sorting nexin 5 lacks phosphatidylinositol 3-phosphate (PtdIns(3)P) specificity and preferentially binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). J Biol Chem 2009; 284:23697-707. [PMID: 19553671 PMCID: PMC2749144 DOI: 10.1074/jbc.m109.008995] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 06/08/2009] [Indexed: 11/06/2022] Open
Abstract
Subcellular retrograde transport of cargo receptors from endosomes to the trans-Golgi network is critically involved in a broad range of physiological and pathological processes and highly regulated by a genetically conserved heteropentameric complex, termed retromer. Among the retromer components identified in mammals, sorting nexin 5 and 1 (SNX5; SNX1) have recently been found to interact, possibly controlling the membrane binding specificity of the complex. To elucidate how the unique sequence features of the SNX5 phox domain (SNX5-PX) influence retrograde transport, we have determined the SNX5-PX structure by NMR and x-ray crystallography at 1.5 A resolution. Although the core fold of SNX5-PX resembles that of other known PX domains, we found novel structural features exclusive to SNX5-PX. It is most noteworthy that in SNX5-PX, a long helical hairpin is added to the core formed by a new alpha2'-helix and a much longer alpha3-helix. This results in a significantly altered overall shape of the protein. In addition, the unique double PXXP motif is tightly packed against the rest of the protein, rendering this part of the structure compact, occluding parts of the putative phosphatidylinositol (PtdIns) binding pocket. The PtdIns binding and specificity of SNX5-PX was evaluated by NMR titrations with eight different PtdIns and revealed that SNX5-PX preferentially and specifically binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). The distinct structural and PtdIns binding characteristics of SNX5-PX impart specific properties on SNX5, influencing retromer-mediated regulation of retrograde trafficking of transmembrane cargo receptors.
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Affiliation(s)
| | - William Furey
- Pharmacology and Chemical Biology
- the Biocrystallography Laboratory, Veterans Affairs Medical Center, Pittsburgh, Pennsylvania 15240
| | | | - Yong-Jian Liu
- Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
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113
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Coon BG, Mukherjee D, Hanna CB, Riese DJ, Lowe M, Aguilar RC. Lowe syndrome patient fibroblasts display Ocrl1-specific cell migration defects that cannot be rescued by the homologous Inpp5b phosphatase. Hum Mol Genet 2009; 18:4478-91. [PMID: 19700499 PMCID: PMC7289333 DOI: 10.1093/hmg/ddp407] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Lowe syndrome (LS) is a life-threatening, developmental disease characterized by mental retardation, cataracts and renal failure. Although this human illness has been linked to defective function of the phosphatidylinositol 5-phosphatase, Ocrl1 (Oculo-Cerebro-Renal syndrome ofLowe protein1), the mechanism by which this enzyme deficiency triggers the disease is not clear. Ocrl1 is known to localize mainly to the Golgi apparatus and endosomes, however it translocates to plasma membrane ruffles upon cell stimulation with growth factors. The functional implications of this inducible translocation to the plasma membrane are presently unknown. Here we show that Ocrl1 is required for proper cell migration, spreading and fluid-phase uptake in both established cell lines and human dermal fibroblasts. We found that primary fibroblasts from two patients diagnosed with LS displayed defects in these cellular processes. Importantly, these abnormalities were suppressed by expressing wild-type Ocrl1 but not by a phosphatase-deficient mutant. Interestingly, the homologous human PI-5-phosphatase, Inpp5b, was unable to complement the Ocrl1-dependent cell migration defect. Further, Ocrl1 variants that cannot bind the endocytic adaptor AP2 or clathrin, like Inpp5b, were less apt to rescue the migration phenotype. However, no defect in membrane recruitment of AP2/clathrin or in transferrin endocytosis by patient cells was detected. Collectively, our results suggest that Ocrl1, but not Inpp5b, is involved in ruffle-mediated membrane remodeling. Our results provide new elements for understanding how Ocrl1 deficiency leads to the abnormalities associated with the LS.
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Affiliation(s)
- Brian G Coon
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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114
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Sasaki T, Takasuga S, Sasaki J, Kofuji S, Eguchi S, Yamazaki M, Suzuki A. Mammalian phosphoinositide kinases and phosphatases. Prog Lipid Res 2009; 48:307-43. [PMID: 19580826 DOI: 10.1016/j.plipres.2009.06.001] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Phosphoinositides are lipids that are present in the cytoplasmic leaflet of a cell's plasma and internal membranes and play pivotal roles in the regulation of a wide variety of cellular processes. Phosphoinositides are molecularly diverse due to variable phosphorylation of the hydroxyl groups of their inositol rings. The rapid and reversible configuration of the seven known phosphoinositide species is controlled by a battery of phosphoinositide kinases and phosphoinositide phosphatases, which are thus critical for phosphoinositide isomer-specific localization and functions. Significantly, a given phosphoinositide generated by different isozymes of these phosphoinositide kinases and phosphatases can have different biological effects. In mammals, close to 50 genes encode the phosphoinositide kinases and phosphoinositide phosphatases that regulate phosphoinositide metabolism and thus allow cells to respond rapidly and effectively to ever-changing environmental cues. Understanding the distinct and overlapping functions of these phosphoinositide-metabolizing enzymes is important for our knowledge of both normal human physiology and the growing list of human diseases whose etiologies involve these proteins. This review summarizes the structural and biological properties of all the known mammalian phosphoinositide kinases and phosphoinositide phosphatases, as well as their associations with human disorders.
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Affiliation(s)
- Takehiko Sasaki
- Department of Pathology and Immunology, Akita University, Graduate School of Medicine, Akita 010-8543, Japan.
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115
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A PH domain within OCRL bridges clathrin-mediated membrane trafficking to phosphoinositide metabolism. EMBO J 2009; 28:1831-42. [PMID: 19536138 DOI: 10.1038/emboj.2009.155] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/13/2009] [Indexed: 11/09/2022] Open
Abstract
OCRL, whose mutations are responsible for Lowe syndrome and Dent disease, and INPP5B are two similar proteins comprising a central inositol 5-phosphatase domain followed by an ASH and a RhoGAP-like domain. Their divergent NH2-terminal portions remain uncharacterized. We show that the NH2-terminal region of OCRL, but not of INPP5B, binds clathrin heavy chain. OCRL, which in contrast to INPP5B visits late stage endocytic clathrin-coated pits, was earlier shown to contain another binding site for clathrin in its COOH-terminal region. NMR structure determination further reveals that despite their primary sequence dissimilarity, the NH2-terminal portions of both OCRL and INPP5B contain a PH domain. The novel clathrin-binding site in OCRL maps to an unusual clathrin-box motif located in a loop of the PH domain, whose mutations reduce recruitment efficiency of OCRL to coated pits. These findings suggest an evolutionary pressure for a specialized function of OCRL in bridging phosphoinositide metabolism to clathrin-dependent membrane trafficking.
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116
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Suchy SF, Cronin JC, Nussbaum RL. Abnormal bradykinin signalling in fibroblasts deficient in the PIP(2) 5-phosphatase, ocrl1. J Inherit Metab Dis 2009; 32:280-8. [PMID: 19172411 DOI: 10.1007/s10545-009-1058-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 12/11/2008] [Accepted: 12/16/2008] [Indexed: 01/01/2023]
Abstract
The oculocerebrorenal syndrome of Lowe (Lowe syndrome) is an X-linked disorder of phosphatidylinositol metabolism characterized by congenital cataracts, renal proximal tubulopathy and neurological deficits. The disorder is due to the deficiency of the phosphatidylinositol 4,5-bisphosphate (PIP(2)) 5-phosphatase, ocrl1. PIP(2) is critical for numerous cellular processes, including cell signalling, actin reorganization and protein trafficking, and is chronically elevated in patients with Lowe syndrome. The elevation of PIP(2) cells of patients with Lowe syndrome provides the unique opportunity to investigate the roles of this phospholipid in fundamental cellular processes. We previously demonstrated that ocrl1 deficiency causes alterations in the actin cytoskeleton. Since actin remodelling is strongly activated by [Ca(+2)], which increases in response to IP(3) production, we hypothesized that altered calcium signalling might contribute to the observed abnormalities in actin organization. Here we report a specific increase in bradykinin-induced Ca(+2) mobilization in Lowe fibroblasts. We show that the abnormal bradykinin signalling occurs in spite of normal total cellular receptor content. These data point to a novel role for ocrl1 in agonist-induced calcium release.
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Affiliation(s)
- S F Suchy
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA.
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McCrea HJ, De Camilli P. Mutations in phosphoinositide metabolizing enzymes and human disease. Physiology (Bethesda) 2009; 24:8-16. [PMID: 19196647 DOI: 10.1152/physiol.00035.2008] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Phosphoinositides are implicated in the regulation of a wide variety of cellular functions. Their importance in cellular and organismal physiology is underscored by the growing number of human diseases linked to perturbation of kinases and phosphatases that catalyze interconversion from one phosphoinositide to another. Many such enzymes are attractive targets for therapeutic interventions. Here, we review diseases linked to inheritable or somatic mutations of these enzymes.
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Affiliation(s)
- Heather J McCrea
- Howard Hughes Medical Institute, Department of Cell Biology, Kavli Institute for Neuroscience, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut, USA
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118
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The role of the inositol polyphosphate 5-phosphatases in cellular function and human disease. Biochem J 2009; 419:29-49. [PMID: 19272022 DOI: 10.1042/bj20081673] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Phosphoinositides are membrane-bound signalling molecules that regulate cell proliferation and survival, cytoskeletal reorganization and vesicular trafficking by recruiting effector proteins to cellular membranes. Growth factor or insulin stimulation induces a canonical cascade resulting in the transient phosphorylation of PtdIns(4,5)P(2) by PI3K (phosphoinositide 3-kinase) to form PtdIns(3,4,5)P(3), which is rapidly dephosphorylated either by PTEN (phosphatase and tensin homologue deleted on chromosome 10) back to PtdIns(4,5)P(2), or by the 5-ptases (inositol polyphosphate 5-phosphatases), generating PtdIns(3,4)P(2). The 5-ptases also hydrolyse PtdIns(4,5)P(2), forming PtdIns4P. Ten mammalian 5-ptases have been identified, which share a catalytic mechanism similar to that of the apurinic/apyrimidinic endonucleases. Gene-targeted deletion of 5-ptases in mice has revealed that these enzymes regulate haemopoietic cell proliferation, synaptic vesicle recycling, insulin signalling, endocytosis, vesicular trafficking and actin polymerization. Several studies have revealed that the molecular basis of Lowe's syndrome is due to mutations in the 5-ptase OCRL (oculocerebrorenal syndrome of Lowe). Futhermore, the 5-ptases SHIP [SH2 (Src homology 2)-domain-containing inositol phosphatase] 2, SKIP (skeletal muscle- and kidney-enriched inositol phosphatase) and 72-5ptase (72 kDa 5-ptase)/Type IV/Inpp5e (inositol polyphosphate 5-phosphatase E) are implicated in negatively regulating insulin signalling and glucose homoeostasis in specific tissues. SHIP2 polymorphisms are associated with a predisposition to insulin resistance. Gene profiling studies have identified changes in the expression of various 5-ptases in specific cancers. In addition, 5-ptases such as SHIP1, SHIP2 and 72-5ptase/Type IV/Inpp5e regulate macrophage phagocytosis, and SHIP1 also controls haemopoietic cell proliferation. Therefore the 5-ptases are a significant family of signal-modulating enzymes that govern a plethora of cellular functions by regulating the levels of specific phosphoinositides. Emerging studies have implicated their loss or gain of function in human disease.
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119
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Choudhury R, Noakes CJ, McKenzie E, Kox C, Lowe M. Differential clathrin binding and subcellular localization of OCRL1 splice isoforms. J Biol Chem 2009; 284:9965-73. [PMID: 19211563 DOI: 10.1074/jbc.m807442200] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutation of the inositol polyphosphate 5-phosphatase OCRL1 causes the X-linked disorder oculocerebrorenal syndrome of Lowe, characterized by defects in the brain, kidneys, and eyes. OCRL1 exists as two splice isoforms that differ by a single exon encoding 8 amino acids. The longer protein, termed isoform a, is the only form in brain, whereas both isoforms are present in all other tissues. The significance of OCRL1 splicing is currently unclear. Given its proximity to a clathrin-binding site, we hypothesized that splicing may alter the clathrin binding properties of OCRL1. Here we show that this is indeed the case. OCRL1 isoform a binds clathrin with higher affinity than isoform b and is significantly more enriched in clathrin-coated trafficking intermediates. We also identify a second clathrin-binding site in OCRL1 that contributes to clathrin binding of both isoforms. Association of OCRL1 with clathrin-coated intermediates requires membrane association through interaction with Rab GTPases but not binding to the clathrin adaptor AP2. Expression of OCRL1 isoform a lacking the 5-phosphatase domain impairs transferrin endocytosis, whereas an equivalent version of isoform b does not. Our results suggest that OCRL1 exists as two functional pools, one participating in clathrin-mediated trafficking events such as endocytosis and another that is much less or not involved in this process.
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Affiliation(s)
- Rawshan Choudhury
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom
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120
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Great expectations for PIP: phosphoinositides as regulators of signaling during development and disease. Dev Cell 2009; 16:12-20. [PMID: 19154715 DOI: 10.1016/j.devcel.2008.12.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Phosphoinositides function as signaling precursors as well as regulators and scaffolds of signaling molecules required for important cellular processes such as membrane trafficking. Although a picture of the biochemical and cell biological functions of phosphoinositides is emerging, less is known about how these functions impact signaling on a broader scale during development. This review summarizes recent work on the role of phosphoinositides in developmental signaling and in a number of diseases and developmental disorders.
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121
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Skånland SS, Wälchli S, Sandvig K. β-arrestins attenuate p38-mediated endosome to Golgi transport. Cell Microbiol 2009; 11:796-807. [PMID: 19159388 DOI: 10.1111/j.1462-5822.2009.01292.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Shiga toxin (Stx) is after endocytosis transported via early endosomes to the Golgi apparatus and endoplasmic reticulum. It is then translocated to the cytosol where it exerts its toxic effect. We recently reported that p38 is required for endosome to Golgi transport of Stx. In the present study, we investigated whether β-arrestins are effectors of this pathway. β-arrestin knockdown led to enhanced Stx transport. A similar phenotype was achieved upon p38 activation. We demonstrate that p38 and β-arrestin act on the same pathway. β-arrestin colocalized with internalized Stx and, interestingly, was recruited to endosomes upon p38 activation. After Stx treatment, p38 and β-arrestin formed a transient complex. From these data we propose that β-arrestin negatively regulates Stx transport via an interaction with activated p38 and attenuation of its signalling. Interestingly, also mannose 6-phosphate receptor transport was regulated by p38 and β-arrestin. β-arrestins therefore seem to regulate an endosome to Golgi pathway used by multiple cargo proteins.
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Affiliation(s)
- Sigrid S Skånland
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway
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122
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Abstract
Retrograde transport, in which proteins and lipids are shuttled between endosomes and biosynthetic/secretory compartments such as the Golgi apparatus, is crucial for a diverse range of cellular functions. Mechanistic studies that explore the molecular machinery involved in this retrograde trafficking route are shedding light on the functions of transport proteins and are providing fresh insights into possible new therapeutic directions.
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Affiliation(s)
- Ludger Johannes
- CNRS UMR144, Centre de Recherche, Traffic, Signaling, and Delivery Laboratory, 75248 Paris Cedex 05, France.
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123
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Martín‐Belmonte F, Rodríguez‐Fraticelli AE. Chapter 3 Acquisition of Membrane Polarity in Epithelial Tube Formation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 274:129-82. [DOI: 10.1016/s1937-6448(08)02003-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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124
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Abstract
Adiponectin, an adipokine secreted by the white adipose tissue, plays an important role in regulating glucose and lipid metabolism and controlling energy homeostasis in insulin-sensitive tissues. A decrease in the circulating level of adiponectin has been linked to insulin resistance, type 2 diabetes, atherosclerosis, and metabolic syndrome. Adiponectin exerts its effects through two membrane receptors, AdipoR1 and AdipoR2. APPL1 is the first identified protein that interacts directly with adiponectin receptors. APPL1 is an adaptor protein with multiple functional domains, the Bin1/amphiphysin/rvs167, pleckstrin homology, and phosphotyrosine binding domains. The PTB domain of APPL1 interacts directly with the intracellular region of adiponectin receptors. Through this interaction, APPL1 mediates adiponectin signaling and its effects on metabolism. APPL1 also functions in insulin-signaling pathway and is an important mediator of adiponectin-dependent insulin sensitization in skeletal muscle. Adiponectin signaling through APPL1 is necessary to exert its anti-inflammatory and cytoprotective effects on endothelial cells. APPL1 also acts as a mediator of other signaling pathways by interacting directly with membrane receptors or signaling proteins, thereby playing critical roles in cell proliferation, apoptosis, cell survival, endosomal trafficking, and chromatin remodeling. This review focuses mainly on our current understanding of adiponectin signaling in various tissues, the role of APPL1 in mediating adiponectin signaling, and also its role in the cross-talk between adiponectin/insulin-signaling pathways.
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Affiliation(s)
- Sathyaseelan S Deepa
- Dept. of Cellular & Structural Biology, Univ. of Texas Health Science Ctr., 7703 Floyd Curl Dr., San Antonio, TX 78229, USA
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125
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Weber SS, Ragaz C, Hilbi H. The inositol polyphosphate 5-phosphatase OCRL1 restricts intracellular growth of Legionella, localizes to the replicative vacuole and binds to the bacterial effector LpnE. Cell Microbiol 2008; 11:442-60. [PMID: 19021631 DOI: 10.1111/j.1462-5822.2008.01266.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Legionella pneumophila, the causative agent of Legionnaires' disease, replicates within a specific vacuole in amoebae and macrophages. To form these 'Legionella-containing vacuoles' (LCVs), the bacteria employ the Icm/Dot type IV secretion system and effector proteins, some of which anchor to the LCV membrane via the host glycolipid phosphatidylinositol 4-phosphate [PtdIns(4)P]. Here we analysed the role of inositol polyphosphate 5-phosphatases (IP5Ps) during L. pneumophila infections. Bacterial replication and LCV formation occurred more efficiently in Dictyostelium discoideum amoebae lacking the IP5P Dd5P4, a homologue of human OCRL1 (Oculocerebrorenal syndrome of Lowe), implicated in retrograde endosome to Golgi trafficking. The phenotype was complemented by Dd5P4 but not the catalytically inactive 5-phosphatase. Ectopically expressed Dd5P4 or OCRL1 localized to LCVs in D. discoideum via an N-terminal domain previously not implicated in membrane targeting, and OCRL1 was also identified on LCVs in macrophages. Dd5P4 was catalytically active on LCVs and accumulated on LCVs harbouring wild-type but not DeltaicmT mutant L. pneumophila. The N-terminal domain of OCRL1 bound L. pneumophila LpnE, a Sel1-like repeat protein involved in LCV formation, which localizes to LCVs and selectively binds PtdIns(3)P. Our results indicate that OCRL1 restricts intracellular growth of L. pneumophila and binds to LCVs in association with LpnE.
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Affiliation(s)
- Stefan S Weber
- Institute of Microbiology, ETH Zürich, Zürich, Switzerland
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Bockenhauer D, Bokenkamp A, van't Hoff W, Levtchenko E, Kist-van Holthe JE, Tasic V, Ludwig M. Renal phenotype in Lowe Syndrome: a selective proximal tubular dysfunction. Clin J Am Soc Nephrol 2008; 3:1430-6. [PMID: 18480301 DOI: 10.2215/cjn.00520108] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES Lowe syndrome is defined by congenital cataracts, mental retardation, and proximal tubulopathy and is due to mutations in OCRL. Recently, mutations in OCRL were found to underlie some patients with Dent disease, characterized by low molecular weight proteinuria, hypercalciuria, and nephrocalcinosis. This phenotypic heterogeneity is poorly understood. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS The renal phenotype of 16 patients with Lowe syndrome (10.9 +/- 7.0 yr) under care of the authors was characterized to define overlap of symptoms with Dent disease and infer clues about OCRL function. Medical charts of patients were reviewed for data regarding glomerular filtration rate and markers of proximal tubular function. RESULTS All patients had low molecular weight proteinuria and albuminuria. Lysosomal enzymuria was elevated in all 11 patients assessed. Fifteen patients had hypercalciuria, and 14 aminoaciduria. Seven patients required bicarbonate and three required phosphate replacement; all others maintained normal serum values without supplementation. None of the patients had detectable glycosuria, and none had clinically overt rickets. GFR was mildly to moderately impaired and highly variable, with a trend of deterioration with age. CONCLUSIONS Patients with Lowe syndrome do not have renal Fanconi syndrome but a selective proximal tubulopathy, variable in extent and dominated by low molecular weight proteinuria and hypercalciuria, the classical features of Dent disease. These findings suggest that OCRL and ClC-5, the chloride channel mutated in Dent disease, are involved in similar reabsorption pathways in the proximal tubule.
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Affiliation(s)
- Detlef Bockenhauer
- Department of Nephrology, Great Ormond Street Hospital, London, United Kingdom.
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127
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Wright J, Morales MM, Sousa-Menzes J, Ornellas D, Sipes J, Cui Y, Cui I, Hulamm P, Cebotaru V, Cebotaru L, Guggino WB, Guggino SE. Transcriptional adaptation to Clcn5 knockout in proximal tubules of mouse kidney. Physiol Genomics 2008; 33:341-54. [DOI: 10.1152/physiolgenomics.00024.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dent disease has multiple defects attributed to proximal tubule malfunction including low-molecular-weight proteinuria, aminoaciduria, phosphaturia, and glycosuria. To understand the changes in kidney function of the Clc5 chloride/proton exchanger gene knockout mouse model of Dent disease, we examined gene expression profiles from proximal S1 and S2 tubules of mouse kidneys. We found many changes in gene expression not known previously to be altered in this disease. Genes involved in lipid metabolism, organ development, and organismal physiological processes had the greatest number of significantly changed transcripts. In addition, genes of catalytic activity and transporter activity also had a great number of changed transcripts. Overall, 720 genes are expressed differentially in the proximal tubules of the Dent Clcn5 knockout mouse model compared with those of control wild-type mice. The fingerprint of these gene changes may help us to understand the phenotype of Dent disease.
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Affiliation(s)
- Jerry Wright
- Department of Physiology, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Marcelo M. Morales
- Instituto de Biophysica Carlos Chagas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jackson Sousa-Menzes
- Instituto de Biophysica Carlos Chagas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Debora Ornellas
- Instituto de Biophysica Carlos Chagas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jennifer Sipes
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Yan Cui
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Isabelle Cui
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Phuson Hulamm
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Valeriu Cebotaru
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Liudmila Cebotaru
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - William B. Guggino
- Instituto de Biophysica Carlos Chagas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Sandra E. Guggino
- Department of Medicine, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
- Department of Physiology, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland
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128
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McCrea HJ, Paradise S, Tomasini L, Addis M, Melis MA, De Matteis MA, De Camilli P. All known patient mutations in the ASH-RhoGAP domains of OCRL affect targeting and APPL1 binding. Biochem Biophys Res Commun 2008; 369:493-9. [PMID: 18307981 PMCID: PMC2442618 DOI: 10.1016/j.bbrc.2008.02.067] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 02/12/2008] [Indexed: 11/17/2022]
Abstract
Mutations in the inositol 5-phosphatase OCRL are responsible for Lowe syndrome, an X-linked disorder characterized by bilateral cataracts, mental retardation, neonatal hypotonia, and renal Fanconi syndrome, and for Dent disease, another X-linked condition characterized by kidney reabsorption defects. We have previously described an interaction of OCRL with the endocytic adaptor APPL1 that links OCRL to protein networks involved in the disease phenotype. Here, we provide new evidence showing that among the interactions which target OCRL to membranes of the endocytic pathway, binding to APPL1 is the only one abolished by all known disease-causing missense mutations in the ASH-RhoGAP domains of the protein. Furthermore, we demonstrate that APPL1 and rab5 independently contribute to recruit OCRL to enlarged endosomes induced by the expression of constitutively active Rab5. Thus, binding to APPL1 helps localize OCRL at specific cellular sites, and disruption of this interaction may play a role in disease.
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Affiliation(s)
- Heather J. McCrea
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Summer Paradise
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Livia Tomasini
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Maria Addis
- Dipartimento di Scienze Biomediche e Biotecnologie, Università di Cagliari, 09134 Cagliari, Italy
| | - Maria Antonietta Melis
- Dipartimento di Scienze Biomediche e Biotecnologie, Università di Cagliari, 09134 Cagliari, Italy
| | | | - Pietro De Camilli
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
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129
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Williams C, Choudhury R, McKenzie E, Lowe M. Targeting of the type II inositol polyphosphate 5-phosphatase INPP5B to the early secretory pathway. J Cell Sci 2007; 120:3941-51. [DOI: 10.1242/jcs.014423] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The inositol polyphosphate 5-phosphatase INPP5B is closely related to the Lowe syndrome protein OCRL1, sharing a similar substrate specificity, domain organisation and an ability to compensate for loss of OCRL1 in knockout mice. The cellular localisation and functions of INPP5B have remained poorly defined until recently, when a role within the endocytic pathway was suggested. Here, we report that INPP5B is also localised to the early secretory pathway including the Golgi apparatus and ER-to-Golgi intermediate compartment (ERGIC). Consistent with this localisation, INPP5B binds to specific RAB proteins within the secretory pathway, and mutational analysis indicates that RAB binding is required for efficient Golgi targeting of INPP5B. Unlike OCRL1, INPP5B interacts with neither clathrin nor α-adaptin and is largely absent from clathrin-coated intermediates. Expression of INPP5B but not OCRL1 alters the distribution of the cycling protein ERGIC53 when cells are incubated at low temperature (15°C) or in the presence of brefeldin A, causing ERGIC53 to accumulate in the ERGIC, with a concomitant loss from the ER. Our data suggest a role for INPP5B in retrograde ERGIC-to-ER transport and imply that it has functions distinct from those of OCRL1 within both the secretory and endocytic pathways.
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Affiliation(s)
- Catrin Williams
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Rawshan Choudhury
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Eddie McKenzie
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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130
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Erdmann KS, Mao Y, McCrea HJ, Zoncu R, Lee S, Paradise S, Modregger J, Biemesderfer D, Toomre D, De Camilli P. A role of the Lowe syndrome protein OCRL in early steps of the endocytic pathway. Dev Cell 2007; 13:377-90. [PMID: 17765681 PMCID: PMC2025683 DOI: 10.1016/j.devcel.2007.08.004] [Citation(s) in RCA: 226] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 05/29/2007] [Accepted: 08/06/2007] [Indexed: 12/26/2022]
Abstract
Mutations in the inositol 5-phosphatase OCRL are responsible for Lowe syndrome, whose manifestations include mental retardation and renal Fanconi syndrome. OCRL has been implicated in membrane trafficking, but disease mechanisms remain unclear. We show that OCRL visits late-stage, endocytic clathrin-coated pits and binds the Rab5 effector APPL1 on peripheral early endosomes. The interaction with APPL1, which is mediated by the ASH-RhoGAP-like domains of OCRL and is abolished by disease mutations, provides a link to protein networks implicated in the reabsorptive function of the kidney and in the trafficking and signaling of growth factor receptors in the brain. Crystallographic studies reveal a role of the ASH-RhoGAP-like domains in positioning the phosphatase domain at the membrane interface and a clathrin box protruding from the RhoGAP-like domain. Our results support a role of OCRL in the early endocytic pathway, consistent with the predominant localization of its preferred substrates, PI(4,5)P(2) and PI(3,4,5)P(3), at the cell surface.
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Affiliation(s)
- Kai S. Erdmann
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Yuxin Mao
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Heather J. McCrea
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Roberto Zoncu
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Department of Neurobiology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Sangyoon Lee
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Summer Paradise
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Jan Modregger
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Daniel Biemesderfer
- Department of Internal Medicine, School of Medicine, Yale University, New Haven, CT 06520
| | - Derek Toomre
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
| | - Pietro De Camilli
- Department of Cell Biology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Department of Neurobiology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience Neurodegeneration and Repair, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06510
- * Correspondence: , telephone: 203 737 4461
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131
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Shin HW, Hayashi M, Christoforidis S, Lacas-Gervais S, Hoepfner S, Wenk MR, Modregger J, Uttenweiler-Joseph S, Wilm M, Nystuen A, Frankel WN, Solimena M, De Camilli P, Zerial M. An enzymatic cascade of Rab5 effectors regulates phosphoinositide turnover in the endocytic pathway. ACTA ACUST UNITED AC 2007; 170:607-18. [PMID: 16103228 PMCID: PMC2171494 DOI: 10.1083/jcb.200505128] [Citation(s) in RCA: 345] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Generation and turnover of phosphoinositides (PIs) must be coordinated in a spatial- and temporal-restricted manner. The small GTPase Rab5 interacts with two PI 3-kinases, Vps34 and PI3Kβ, suggesting that it regulates the production of 3-PIs at various stages of the early endocytic pathway. Here, we discovered that Rab5 also interacts directly with PI 5- and PI 4-phosphatases and stimulates their activity. Rab5 regulates the production of phosphatidylinositol 3-phosphate (PtdIns[3]P) through a dual mechanism, by directly phosphorylating phosphatidylinositol via Vps34 and by a hierarchical enzymatic cascade of phosphoinositide-3-kinaseβ (PI3Kβ), PI 5-, and PI 4-phosphatases. The functional importance of such an enzymatic pathway is demonstrated by the inhibition of transferrin uptake upon silencing of PI 4-phosphatase and studies in weeble mutant mice, where deficiency of PI 4-phosphatase causes an increase of PtdIns(3,4)P2 and a reduction in PtdIns(3)P. Activation of PI 3-kinase at the plasma membrane is accompanied by the recruitment of Rab5, PI 4-, and PI 5-phosphatases to the cell cortex. Our data provide the first evidence for a dual role of a Rab GTPase in regulating both generation and turnover of PIs via PI kinases and phosphatases to coordinate signaling functions with organelle homeostasis.
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Affiliation(s)
- Hye-Won Shin
- Max-Planck Institute of Molecular Cell Biology and Genetics, 01307, Dresden, Germany
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Young A. Structural insights into the clathrin coat. Semin Cell Dev Biol 2007; 18:448-58. [PMID: 17702618 DOI: 10.1016/j.semcdb.2007.07.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 07/05/2007] [Indexed: 11/25/2022]
Abstract
Clathrin is a cytoplasmic protein best known for its role in endocytosis and intracellular trafficking. The diverse nature of clathrin has recently become apparent, with strong evidence available suggesting roles in both chromosome segregation and reassembly of the Golgi apparatus during mitosis. Clathrin functions as a heterohexamer, adopting a three-legged triskelion structure of three clathrin light chains and three heavy chains. During endocytosis clathrin forms a supportive network about the invaginating membrane, interacting with itself and numerous adapter proteins. Advances in the field of structural biology have led us to a greater understanding of clathrin in its assembled state, the clathrin lattice. Combining techniques such as X-ray crystallography, NMR, and cryo-electron microscopy has allowed us to piece together the intricate nature of clathrin-coated vesicles and the interactions of clathrin with its many binding partners. In this review I outline the roles of clathrin within the cell and the recent structural advances that have improved our understanding of clathrin-clathrin and clathrin-protein interactions.
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Affiliation(s)
- Anna Young
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, West Midlands, UK.
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133
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Heck JN, Mellman DL, Ling K, Sun Y, Wagoner MP, Schill NJ, Anderson RA. A conspicuous connection: structure defines function for the phosphatidylinositol-phosphate kinase family. Crit Rev Biochem Mol Biol 2007; 42:15-39. [PMID: 17364683 DOI: 10.1080/10409230601162752] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The phosphatidylinositol phosphate (PIP) kinases are a unique family of enzymes that generate an assortment of lipid messengers, including the pivotal second messenger phosphatidylinositol 4,5-bisphosphate (PI4,5P2). While members of the PIP kinase family function by catalyzing a similar phosphorylation reaction, the specificity loop of each PIP kinase subfamily determines substrate preference and partially influences distinct subcellular targeting. Specific protein-protein interactions that are unique to particular isoforms or splice variants play a key role in targeting PIP kinases to appropriate subcellular compartments to facilitate the localized generation of PI4,5P2 proximal to effectors, a mechanism key for the function of PI4,5P2 as a second messenger. This review documents the discovery of the PIP kinases and their signaling products, and summarizes our current understanding of the mechanisms underlying the localized generation of PI4,5P2 by PIP kinases for the regulation of cellular events including actin cytoskeleton dynamics, vesicular trafficking, cell migration, and an assortment of nuclear events.
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Affiliation(s)
- Jessica N Heck
- Program in Molecular and Cellular Pharmacology, Department of Pharmacology, University of Wisconsin-Madison, University of Wisconsin Medical School, Madison, WI 53706, USA
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134
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Fuchs E, Haas AK, Spooner RA, Yoshimura SI, Lord JM, Barr FA. Specific Rab GTPase-activating proteins define the Shiga toxin and epidermal growth factor uptake pathways. ACTA ACUST UNITED AC 2007; 177:1133-43. [PMID: 17562788 PMCID: PMC2064371 DOI: 10.1083/jcb.200612068] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Rab family guanosine triphosphatases (GTPases) together with their regulators define specific pathways of membrane traffic within eukaryotic cells. In this study, we have investigated which Rab GTPase-activating proteins (GAPs) can interfere with the trafficking of Shiga toxin from the cell surface to the Golgi apparatus and studied transport of the epidermal growth factor (EGF) from the cell surface to endosomes. This screen identifies 6 (EVI5, RN-tre/USP6NL, TBC1D10A–C, and TBC1D17) of 39 predicted human Rab GAPs as specific regulators of Shiga toxin but not EGF uptake. We show that Rab43 is the target of RN-tre and is required for Shiga toxin uptake. In contrast, RabGAP-5, a Rab5 GAP, was unique among the GAPs tested and reduced the uptake of EGF but not Shiga toxin. These results suggest that Shiga toxin trafficking to the Golgi is a multistep process controlled by several Rab GAPs and their target Rabs and that this process is discrete from ligand-induced EGF receptor trafficking.
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Affiliation(s)
- Evelyn Fuchs
- Department of Cell Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany
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135
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Vilasi A, Cutillas PR, Maher AD, Zirah SFM, Capasso G, Norden AWG, Holmes E, Nicholson JK, Unwin RJ. Combined proteomic and metabonomic studies in three genetic forms of the renal Fanconi syndrome. Am J Physiol Renal Physiol 2007; 293:F456-67. [PMID: 17494094 DOI: 10.1152/ajprenal.00095.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The renal Fanconi syndrome is a defect of proximal tubular function causing aminoaciduria and low-molecular-weight proteinuria. Dent's disease and Lowe syndrome are defined X-linked forms of Fanconi syndrome; there is also an autosomal dominant idiopathic form (ADIF), phenotypically similar to Dent's disease though its gene defect is still unknown. To assess whether their respective gene products are ultimately involved in a common reabsorptive pathway for proteins and low-molecular-mass endogenous metabolites, we compared renal Fanconi urinary proteomes and metabonomes with normal (control) urine using mass spectrometry and (1)H-NMR spectroscopy, respectively. Urine from patients with low-molecular-weight proteinuria secondary to ifosfamide treatment (tubular proteinuria; TP) was also analyzed for comparison. All four of the disorders studied had characteristic proteomic and metabonomic profiles. Uromodulin was the most abundant protein in normal urine, whereas Fanconi urine was dominated by albumin. (1)H-NMR spectroscopic data showed differences in the metabolic profiles of Fanconi urine vs. normal urine, due mainly to aminoaciduria. There were differences in the urinary metabolite and protein compositions between the three genetic forms of Fanconi syndrome: cluster analysis grouped the Lowe and Dent's urinary proteomes and metabonomes together, whereas ADIF and TP clustered together separately. Our findings demonstrate a distinctive "polypeptide and metabolite fingerprint" that can characterize the renal Fanconi syndrome; they also suggest that more subtle and cause-specific differences may exist between the different forms of Fanconi syndrome that might provide novel insights into the underlying mechanisms and cellular pathways affected.
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136
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Olkkonen VM, Ikonen E. When intracellular logistics fails--genetic defects in membrane trafficking. J Cell Sci 2007; 119:5031-45. [PMID: 17158910 DOI: 10.1242/jcs.03303] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The number of human genetic disorders shown to be due to defects in membrane trafficking has greatly increased during the past five years. Defects have been identified in components involved in sorting of cargo into transport carriers, vesicle budding and scission, movement of vesicles along cytoskeletal tracks, as well as in vesicle tethering, docking and fusion at the target membrane. The nervous system is extremely sensitive to such disturbances of the membrane trafficking machinery, and the majority of these disorders display neurological defects--particularly diseases affecting the motility of transport carriers along cytoskeletal tracks. In several disorders, defects in a component that represents a fundamental part of the trafficking machinery fail to cause global transport defects but result in symptoms limited to specific cell types and transport events; this apparently reflects the redundancy of the transport apparatus. In groups of closely related diseases such as Hermansky-Pudlak and Griscelli syndromes, identification of the underlying gene defects has revealed groups of genes in which mutations lead to similar phenotypic consequences. New functionally linked trafficking components and regulatory mechanisms have thus been discovered. Studies of the gene defects in trafficking disorders therefore not only open avenues for new therapeutic approaches but also significantly contribute to our knowledge of the fundamental mechanisms of intracellular membrane transport.
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Affiliation(s)
- Vesa M Olkkonen
- Department of Molecular Medicine, National Public Health Institute (KTL), Biomedicum, POBox 104, FI-00251 Helsinki, Finland.
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137
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Loovers HM, Kortholt A, de Groote H, Whitty L, Nussbaum RL, van Haastert PJM. Regulation of Phagocytosis in Dictyostelium by the Inositol 5-Phosphatase OCRL Homolog Dd5P4. Traffic 2007; 8:618-28. [PMID: 17343681 DOI: 10.1111/j.1600-0854.2007.00546.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphoinositides are involved in endocytosis in both mammalian cells and the amoeba Dictyostelium discoideum. Dd5P4 is the Dictyostelium homolog of human OCRL (oculocerebrorenal syndrome of Lowe); both have a RhoGAP domain and a 5-phosphatase domain that acts on phosphatidylinositol 4,5-bisphosphate/phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3). Inactivation of Dd5P4 inhibits growth on liquid medium and on bacteria. Dd5p4-null cells are impaired in phagocytosis of yeast cells. In wild-type cells, PI(3,4,5)P3 is formed and converted to PI(3,4)P2 just before closure of the phagocytic cup. In dd5p4-null cells, a phagocytic cup is formed upon contact with the yeast cell, and PI(3,4,5)P3 is still produced, but the phagocytic cup does not close. We suggest that Dd5P4 regulates the conversion of PI(3,4,5)P3 to PI(3,4)P2 and that this conversion is essential for closure of the phagocytic cup. Phylogenetic analysis of OCRL-like 5-phosphatases with RhoGAP domains reveal that D. discoideum Dd5P4 is a surprisingly close homolog of human OCRL, the protein responsible for Lowe syndrome. We expressed human OCRL in dd5p4-null cells. Growth on bacteria and axenic medium is largely restored, whereas the rate of phagocytosis of yeast cells is partly restored, indicating that human OCRL can functionally replace Dictyostelium Dd5P4.
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Affiliation(s)
- Harriët M Loovers
- Department of Molecular Cell Biology, University of Groningen, Kerklaan 30, 9751NN Haren, The Netherlands
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138
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Howell GJ, Holloway ZG, Cobbold C, Monaco AP, Ponnambalam S. Cell biology of membrane trafficking in human disease. ACTA ACUST UNITED AC 2007; 252:1-69. [PMID: 16984815 PMCID: PMC7112332 DOI: 10.1016/s0074-7696(06)52005-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Understanding the molecular and cellular mechanisms underlying membrane traffic pathways is crucial to the treatment and cure of human disease. Various human diseases caused by changes in cellular homeostasis arise through a single gene mutation(s) resulting in compromised membrane trafficking. Many pathogenic agents such as viruses, bacteria, or parasites have evolved mechanisms to subvert the host cell response to infection, or have hijacked cellular mechanisms to proliferate and ensure pathogen survival. Understanding the consequence of genetic mutations or pathogenic infection on membrane traffic has also enabled greater understanding of the interactions between organisms and the surrounding environment. This review focuses on human genetic defects and molecular mechanisms that underlie eukaryote exocytosis and endocytosis and current and future prospects for alleviation of a variety of human diseases.
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Affiliation(s)
- Gareth J Howell
- Endothelial Cell Biology Unit, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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139
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Mukhopadhyay S, Xu F, Sehgal PB. Aberrant cytoplasmic sequestration of eNOS in endothelial cells after monocrotaline, hypoxia, and senescence: live-cell caveolar and cytoplasmic NO imaging. Am J Physiol Heart Circ Physiol 2006; 292:H1373-89. [PMID: 17071725 DOI: 10.1152/ajpheart.00990.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously reported the disruption of caveolae/rafts, dysfunction of Golgi tethers, N-ethylmaleimide-sensitive factor-attachment protein (SNAP) receptor proteins (SNAREs), and SNAPs, and inhibition of anterograde trafficking in endothelial cells in culture and rat lung exposed to monocrotaline pyrrole (MCTP) as a prelude to the development of pulmonary hypertension. We have now investigated 1) whether this trafficking block affects subcellular localization and function of endothelial nitric oxide (NO) synthase (eNOS) and 2) whether Golgi blockade and eNOS sequestration are observed after hypoxia and senescence. Immunofluorescence data revealed that MCTP-induced "megalocytosis" of pulmonary arterial endothelial cells (PAEC) was accompanied by a loss of eNOS from the plasma membrane, with increased accumulation in the cytoplasm. This cytoplasmic eNOS was sequestered in heterogeneous compartments and partially colocalized with Golgi and endoplasmic reticulum (ER) markers, caveolin-1, NOSTRIN, and ER Tracker, but not Lyso Tracker. Hypoxia and senescence also produced enlarged PAEC, with dysfunctional Golgi and loss of eNOS from the plasma membrane, with sequestration in the cytoplasm. Live-cell imaging of caveolar and cytoplasmic NO with 4,5-diaminofluorescein diacetate (DAF-2DA) as probe showed a marked loss of caveolar NO after MCTP, hypoxia, and senescence. Although ionomycin stimulated DAF-2DA fluorescence in control PAEC, this ionophore decreased DAF-2DA fluorescence in MCTP-treated and senescent PAEC, suggesting localization of eNOS in an aberrant cytoplasmic compartment that was readily discharged by Ca(2+)-induced exocytosis. Thus monocrotaline, hypoxia, and senescence produce a Golgi blockade in PAEC, leading to sequestration of eNOS away from its functional caveolar location and providing a mechanism for the often-reported reduction in pulmonary arterial NO levels in experimental pulmonary hypertension, despite sustained eNOS protein levels.
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140
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Bonifacino JS, Rojas R. Retrograde transport from endosomes to the trans-Golgi network. Nat Rev Mol Cell Biol 2006; 7:568-79. [PMID: 16936697 DOI: 10.1038/nrm1985] [Citation(s) in RCA: 486] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A subset of intracellular transmembrane proteins such as acid-hydrolase receptors, processing peptidases and SNAREs, as well as extracellular protein toxins such as Shiga toxin and ricin, undergoes 'retrograde' transport from endosomes to the trans-Golgi network. Here, we discuss recent studies that have begun to unravel the molecular machinery that is involved in this process. We also propose a central role for a 'tubular endosomal network' in sorting to recycling pathways that lead not only to the trans-Golgi network but also to different plasma-membrane domains and to specialized storage vesicles.
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Affiliation(s)
- Juan S Bonifacino
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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141
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Abstract
Phosphoinositide metabolism plays a pivotal role in the regulation of receptor-mediated signal transduction, actin remodelling and membrane dynamics. Phosphoinositides co-ordinate these processes by recruiting protein effectors to distinct cellular membranes in a time- and organelle-dependent manner. Intracellular bacterial pathogens interfere with phosphoinositide metabolism to direct their entry into eukaryotic cells, form replication-permissive vacuoles, modulate apoptosis, or trigger fluid secretion. Gram-negative pathogens such as Legionella pneumophila, Shigella flexneri, or Salmonella enterica employ secretion systems to invade host cells by 'pathogen-triggered phagocytosis' and thereby bypass a requirement for phosphatidylinositol 3-kinases [PI(3)Ks]. Contrarily, 'receptor-mediated phagocytosis' of Yersinia spp., Listeria monocytogenes and other pathogenic bacteria depends on PI(3)Ks. Secreted effector proteins have been found to directly bind to and modify host cell phosphoinositides, thus modulating phagocytosis and intracellular survival of the pathogens. These effectors include L. pneumophila proteins that specifically attach to phosphatidylinositol 4-phosphate [PI(4)P] on the Legionella-containing vacuole, and phosphoinositide phosphatases produced by S. flexneri, S. enterica or Mycobacterium tuberculosis. This review covers current knowledge about subversion of host cell phosphoinositide metabolism by intracellular bacterial pathogens with an emphasis on recently identified secreted effector proteins directly engaging phosphoinositides.
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Affiliation(s)
- Hubert Hilbi
- Institute of Microbiology, ETH Zürich, Wolfgang-Pauli Strasse 10, 8093 Zürich, Switzerland.
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142
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Hyvola N, Diao A, McKenzie E, Skippen A, Cockcroft S, Lowe M. Membrane targeting and activation of the Lowe syndrome protein OCRL1 by rab GTPases. EMBO J 2006; 25:3750-61. [PMID: 16902405 PMCID: PMC1553191 DOI: 10.1038/sj.emboj.7601274] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Accepted: 07/13/2006] [Indexed: 01/15/2023] Open
Abstract
The X-linked disorder oculocerebrorenal syndrome of Lowe is caused by mutation of the OCRL1 protein, an inositol polyphosphate 5-phosphatase. OCRL1 is localised to the Golgi apparatus and early endosomes, and can translocate to lamellipodia upon growth factor stimulation. We show here that OCRL1 interacts with several members of the rab family of small GTPases. Strongest interaction is seen with Golgi-associated rab1 and rab6 and endosomal rab5. Point mutants defective in rab binding fail to target to the Golgi apparatus and endosomes, strongly suggesting rab interaction is required for targeting of OCRL1 to these compartments. Membrane recruitment via rab binding is required for changes in Golgi and endosomal dynamics induced by overexpression of catalytically inactive OCRL1. In vitro experiments demonstrate that rab5 and rab6 directly stimulate the 5-phosphatase activity of OCRL1. We conclude that rabs play a dual role in regulation of OCRL1, firstly targeting it to the Golgi apparatus and endosomes, and secondly, directly stimulating the 5-phosphatase activity of OCRL1 after membrane recruitment.
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Affiliation(s)
- Noora Hyvola
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, UK
| | - Aipo Diao
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, UK
| | - Eddie McKenzie
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, UK
| | - Alison Skippen
- Department of Physiology, University College London, London, UK
| | | | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, UK
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143
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Utskarpen A, Slagsvold HH, Iversen TG, Wälchli S, Sandvig K. Transport of Ricin from Endosomes to the Golgi Apparatus is Regulated by Rab6A and Rab6A′. Traffic 2006; 7:663-72. [PMID: 16683916 DOI: 10.1111/j.1600-0854.2006.00418.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ricin is transported from early endosomes and/or the recycling compartment to the trans-Golgi network (TGN) and subsequently to the endoplasmic recticulum (ER) before it enters the cytosol and intoxicates cells. We have investigated the role of the Rab6 isoforms in retrograde transport of ricin using both oligo- and vector-based RNAi assays. Ricin transport to the TGN was inhibited by the depletion of Rab6A when the Rab6A messenger RNA (mRNA) levels were reduced by more than 40% and less than 75%. However, when Rab6A mRNA was reduced by more than 75% and Rab6A' mRNA was simultaneously up-regulated, the inhibition of ricin sulfation was abolished, indicating that the up-regulation of Rab6A' may compensate for the loss of Rab6A function. In addition, we found that a near complete depletion of Rab6A' gave approximately 40% reduction in ricin sulfation. The up-regulation of Rab6A mRNA levels did not seem to compensate for the loss of Rab6A' function. The depletion of both Rab6A and Rab6A' gave a stronger inhibition of ricin sulfation than what was observed knocking down the two isoforms separately. In conclusion, both Rab6A and Rab6A' seem to be involved in the transport of ricin from endosomes to the Golgi apparatus.
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Affiliation(s)
- Audrun Utskarpen
- Department of Biochemistry, Institute for Cancer Research, Faculty Division The Norwegian Radium Hospital, University of Oslo, Montebello, 0310 Oslo, Norway
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144
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Guerriero CJ, Weixel KM, Bruns JR, Weisz OA. Phosphatidylinositol 5-kinase stimulates apical biosynthetic delivery via an Arp2/3-dependent mechanism. J Biol Chem 2006; 281:15376-84. [PMID: 16601114 DOI: 10.1074/jbc.m601239200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The mechanisms by which polarized epithelial cells target distinct carriers enriched in newly synthesized proteins to the apical or basolateral membrane remain largely unknown. Here we investigated the effect of phosphatidylinositol metabolism and modulation of the actin cytoskeleton, two regulatory mechanisms that have individually been suggested to function in biosynthetic traffic, on polarized traffic in Madin-Darby canine kidney cells. Overexpression of phosphatidylinositol 5-kinase (PI5K) increased actin comet frequency in Madin-Darby canine kidney cells and concomitantly stimulated trans-Golgi network (TGN) to apical membrane delivery of the raft-associated protein influenza hemagglutinin (HA), but did not affect delivery of a non-raft-associated apical protein or a basolateral marker. Modulation of actin comet formation by pharmacologic means, by overexpression of the TGN-localized inositol polyphosphate 5-phosphatase Ocrl, or by blockade of Arp2/3 function had parallel effects on the rate of apical delivery of HA. Moreover, HA released from a TGN block was colocalized in transport carriers in association with PI5K and actin comets. Inhibition of Arp2/3 function in combination with microtubule depolymerization led to a virtual block in HA delivery, suggesting synergistic coordination of these cytoskeletal assemblies in membrane transport. Our results suggest a previously unidentified role for actin comet-mediated propulsion in the biosynthetic delivery of a subset of apical proteins.
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Affiliation(s)
- Christopher J Guerriero
- Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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145
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Halstead JR, Jalink K, Divecha N. An emerging role for PtdIns(4,5)P2-mediated signalling in human disease. Trends Pharmacol Sci 2005; 26:654-60. [PMID: 16253350 DOI: 10.1016/j.tips.2005.10.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 09/05/2005] [Accepted: 10/06/2005] [Indexed: 11/18/2022]
Abstract
Although an established regulator of many cellular functions, the phosphoinositide phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P2) appears to have evaded the attention of drug-discovery companies. An increasing number of reports have identified potential links between PtdIns(4,5)P2-mediated signalling pathways and the aetiology of many human diseases. Here, we review current knowledge of the regulation and function of PtdIns(4,5)P2 and discuss how aberrant PtdIns(4,5)P2-mediated signalling might contribute to human pathologies such as cardiac failure, bipolar disorder, channelopathies and the genetic disorder Lowe syndrome.
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Affiliation(s)
- Jonathan R Halstead
- Department of Cellular Biochemistry, the Netherlands Cancer Institute, AvL ziekenhuis, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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