Calnuc Binds to LRP9 and Affects its Endosomal Sorting

Brodeur, Jean‐Marc; Larkin, Heidi; Boucher, Rémi; Thériault, Catherine; St-Louis, Samuel Chayer; Gagnon, Hugo; Lavoie, Christine

doi:10.1111/j.1600-0854.2009.00933.x

Cited by 27 publications

(44 citation statements)

References 58 publications

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“…This suggested that the time of residence of APP in the TGN is prolonged by either the retention of APP molecules en route through the TGN to the cell surface or by the retrograde transport of internalized APP from the endosomes to the TGN. The second possibility is in line with a proposed role for LRP10 in endosome-to-Golgi trafficking [13,21]. However, there were no clear differences in the appearance of internalized APP in the TGN of HeLa cells transfected with APP in the absence or presence of LRP10 wt , suggesting that LRP10 may control the exit of APP from the TGN.…”

Section: Discussionsupporting

confidence: 68%

LDLR-related protein 10 (LRP10) regulates amyloid precursor protein (APP) trafficking and processing: evidence for a role in Alzheimer’s disease

Brodeur

Thériault

Lessard‐Beaudoin

et al. 2012

Mol Neurodegeneration

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BackgroundThe Aβ peptide that accumulates in Alzheimer’s disease (AD) is derived from amyloid precursor protein (APP) following proteolysis by β- and γ-secretases. Substantial evidence indicates that alterations in APP trafficking within the secretory and endocytic pathways directly impact the interaction of APP with these secretases and subsequent Aβ production. Various members of the low-density lipoprotein receptor (LDLR) family have been reported to play a role in APP trafficking and processing and are important risk factors in AD. We recently characterized a distinct member of the LDLR family called LDLR-related protein 10 (LRP10) that shuttles between the trans-Golgi Network (TGN), plasma membrane (PM), and endosomes. Here we investigated whether LRP10 participates in APP intracellular trafficking and Aβ production.ResultsIn this report, we provide evidence that LRP10 is a functional APP receptor involved in APP trafficking and processing. LRP10 interacts directly with the ectodomain of APP and colocalizes with APP at the TGN. Increased expression of LRP10 in human neuroblastoma SH-SY5Y cells induces the accumulation of mature APP in the Golgi and reduces its presence at the cell surface and its processing into Aβ, while knockdown of LRP10 expression increases Aβ production. Mutations of key motifs responsible for the recycling of LRP10 to the TGN results in the aberrant redistribution of APP with LRP10 to early endosomes and a concomitant increase in APP β-cleavage into Aβ. Furthermore, expression of LRP10 is significantly lower in the post-mortem brain tissues of AD patients, supporting a possible role for LRP10 in AD.ConclusionsThe present study identified LRP10 as a novel APP sorting receptor that protects APP from amyloidogenic processing, suggesting that a decrease in LRP10 function may contribute to the pathogenesis of Alzheimer’s disease.

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Section: Discussionsupporting

confidence: 68%

LDLR-related protein 10 (LRP10) regulates amyloid precursor protein (APP) trafficking and processing: evidence for a role in Alzheimer’s disease

Brodeur

Thériault

Lessard‐Beaudoin

et al. 2012

Mol Neurodegeneration

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“…The detection signal of endogenous TMPRSS6 in HepG2 and human primary hepatocytes was amplified with the TSA TM kit. Treatment with Lysosomal Inhibitors-Cells were incubated for 6 h at 37°C in complete DMEM containing 1 mg/ml leupeptin, 10 g/ml E-64 (HEK293 cells) or E-64d (hepatocytes), and 70 g/ml pepstatin as described previously (21).…”

Section: Methodsmentioning

confidence: 99%

“…Cells were then washed and incubated in complete DMEM at 37°C for various periods of time. The protocol for cell preparation has been described previously (21). The detection signal of endogenous TMPRSS6 in HepG2 and human primary hepatocytes was amplified with the TSA TM kit.…”

Section: Methodsmentioning

confidence: 99%

Essential Role of Endocytosis of the Type II Transmembrane Serine Protease TMPRSS6 in Regulating Its Functionality

Béliveau

Brulé

Désilets

et al. 2011

Journal of Biological Chemistry

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The type II transmembrane serine protease TMPRSS6 (also known as matriptase-2) controls iron homeostasis through its negative regulation of expression of hepcidin, a key hormone involved in iron metabolism. Upstream of the hepcidin-regulated signaling pathway, TMPRSS6 cleaves its target substrate hemojuvelin (HJV) at the plasma membrane, but the dynamics of the cell-surface expression of the protease have not been addressed. Here, we report that TMPRSS6 undergoes constitutive internalization in transfected HEK293 cells and in two human hepatic cell lines, HepG2 and primary hepatocytes, both of which express TMPRSS6 endogenously. Cell surface-labeled TMPRSS6 was internalized and was detected in clathrin-and AP-2-positive vesicles via a dynamin-dependent pathway. The endocytosed TMPRSS6 next transited in early endosomes and then to lysosomes. Internalization of TMPRSS6 is dependent on specific residues within its N-terminal cytoplasmic domain, as site-directed mutagenesis of these residues abrogated internalization and maintained the enzyme at the cell surface. Cells coexpressing these mutants and HJV produced significantly decreased levels of hepcidin compared with wild-type TMPRSS6 due to the sustained cleavage of HJV at the cell surface by TMPRSS6 mutants. Our results underscore for the first time the importance of TMPRSS6 trafficking at the plasma membrane in the regulation of hepcidin expression, an event that is essential for iron homeostasis.The serine protease superfamily of hydrolytic enzymes is composed of Ͼ200 members (MEROPS Database (1)), most of them being secreted soluble proteins. TMPRSS6 (matriptase-2), a member of a novel family of type II transmembrane serine proteases that function at the cell surface (2), was originally characterized as a protease expressed mostly in the liver (3) and capable of processing proteins such as type I collagen, fibronectin, and fibrinogen (4, 5). The protease is a mosaic protein composed of multiple domains, including a 52-residue N-terminal cytoplasmic domain (6), a transmembrane domain that anchors the enzyme within membranes, and an extracellular domain itself constituted of multiple regions, including the catalytic region. Until now, no function had been associated with the cytoplasmic tail of the enzyme. TMPRSS6 is synthesized as an inactive zymogen with the catalytic region being disulfidelinked to the main chain following activation. Moreover, the enzyme undergoes cell-surface shedding, releasing a soluble and active form in the extracellular milieu (7). It exhibits many of the enzymatic specificities of other members of the type II transmembrane serine protease family, preferring arginine residues in P4, P3, and P1 positions relative to the cleaved peptide bond (5,8).Although TMPRSS6 has been associated with breast and prostate cancer (9, 10), recent reports have demonstrated its direct involvement in iron homeostasis. Indeed, genetic analysis of kindred suffering from iron-refractory iron deficiency anemia identified sequence variants in the TMPRSS6 gene, ...

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“…The ubiquitous expression of NUCB1 in various cell and tissue types results in a diverse interactome, including interacting partners like G protein ␣ subunits, cyclooxygenases, and amyloid precursor protein (16,(25)(26)(27). Several classes of G␣ subunits have been shown to interact with NUCB1 (16,(25)(26)(27). Yeast two-hybrid experiments performed with various deletion constructs of either G␣ i3 or NUCB1 mapped the C-terminal ␣5 helix domain of the G protein and the acidic region of NUCB1 (residues 264 -305) to be necessary for interaction (28).…”

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confidence: 99%

Nucleobindin 1 Is a Calcium-regulated Guanine Nucleotide Dissociation Inhibitor of Gαi1

Kapoor

Gupta

Menon

et al. 2010

Journal of Biological Chemistry

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Nucleobindin 1 (NUCB1) is a widely expressed multidomain calcium-binding protein whose precise physiological and biochemical functions are not well understood. We engineered and heterologously expressed a soluble form of NUCB1 (sNUCB1) and characterized its biophysical and biochemical properties. We show that sNUCB1 exists as a dimer in solution and that each monomer binds two divalent calcium cations. Calcium binding causes conformational changes in sNUCB1 as judged by circular dichroism and fluorescence spectroscopy experiments. Earlier reports suggested that NUCB1 might interact with heterotrimeric G protein ␣ subunits. We show that dimeric calcium-free sNUCB1 binds to expressed G␣ i1 and that calcium binding inhibits the interaction. The binding of sNUCB1 to G␣ i1 inhibits its basal rate of GDP release and slows its rate and extent of GTP␥S uptake. Additionally, our tissue culture experiments show that sNUCB1 prevents receptor-mediated G␣ i -dependent inhibition of adenylyl cyclase. Thus, we conclude that sNUCB1 is a calcium-dependent guanine nucleotide dissociation inhibitor (GDI) for G␣ i1 . To our knowledge, sNUCB1 is the first example of a calcium-dependent GDI for heterotrimeric G proteins. We also show that the mechanism of GDI activity of sNUCB1 is unique and does not arise from the consensus GoLoco motif found in RGS proteins. We propose that cytoplasmic NUCB1 might function to regulate heterotrimeric G protein trafficking and G protein-coupled receptor-mediated signal transduction pathways.Heterotrimeric guanine nucleotide-binding proteins, G proteins, couple to heptahelical cell surface G protein-coupled receptors (GPCRs) 3 and participate in intracellular signaling events. The G protein heterotrimer is composed of the G␣ subunit and the G␤␥ heterodimer. Upon ligand-mediated activation, GPCRs catalyze the exchange of GDP for GTP on G␣ leading to dissociation of the heterotrimer into G␣⅐GTP and G␤␥ subunits (1-3). These individual subunits then regulate downstream signaling cascades involving effector systems like adenylyl cyclases, Ca 2ϩ and K ϩ channels, phospholipase C isozymes, and cyclic nucleotide phosphodiesterases (4, 5). Thereafter, the intrinsic GTPase activity of G␣ reverts it back to the GDP-bound state, which can reassociate with G␤␥. This inhibits the interaction of G protein subunits with downstream effectors, which results in the turning-off of the signaling pathways. Hence, signaling by heterotrimeric G proteins is directly dependent on the lifetime of the GTP-bound state of G␣. This lifetime is regulated by GTPase-accelerating proteins (GAPs), which catalyze the rapid hydrolysis of the G␣-bound GTP to GDP and by guanine nucleotide dissociation inhibitors (GDIs), which inhibit the exchange of GDP for GTP in the catalytic pocket of G␣ (6).Together, GAPs and GDIs exert a regulatory control on G protein signaling. In recent years, novel interacting partners of heterotrimeric G proteins called the regulators of G protein signaling or RGS proteins have been discovered that possess GAP ...

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Calnuc Binds to LRP9 and Affects its Endosomal Sorting

Cited by 27 publications

References 58 publications

LDLR-related protein 10 (LRP10) regulates amyloid precursor protein (APP) trafficking and processing: evidence for a role in Alzheimer’s disease

LDLR-related protein 10 (LRP10) regulates amyloid precursor protein (APP) trafficking and processing: evidence for a role in Alzheimer’s disease

Essential Role of Endocytosis of the Type II Transmembrane Serine Protease TMPRSS6 in Regulating Its Functionality

Nucleobindin 1 Is a Calcium-regulated Guanine Nucleotide Dissociation Inhibitor of Gαi1

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