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1.
Cell Rep ; 41(4): 111538, 2022 10 25.
Artigo em Inglês | MEDLINE | ID: mdl-36288700

RESUMO

Accumulating evidence suggests that protein S-nitrosylation is enzymatically regulated and that specificity in S-nitrosylation derives from dedicated S-nitrosylases and denitrosylases that conjugate and remove S-nitrosothiols, respectively. Here, we report that mice deficient in the protein denitrosylase SCoR2 (S-nitroso-Coenzyme A Reductase 2; AKR1A1) exhibit marked reductions in serum cholesterol due to reduced secretion of the cholesterol-regulating protein PCSK9. SCoR2 associates with endoplasmic reticulum (ER) secretory machinery to control an S-nitrosylation cascade involving ER cargo-selection proteins SAR1 and SURF4, which moonlight as S-nitrosylases. SAR1 acts as a SURF4 nitrosylase and SURF4 as a PCSK9 nitrosylase to inhibit PCSK9 secretion, while SCoR2 counteracts nitrosylase activity by promoting PCSK9 denitrosylation. Inhibition of PCSK9 by an NO-based drug requires nitrosylase activity, and small-molecule inhibition of SCoR2 phenocopies the PCSK9-mediated reductions in cholesterol observed in SCoR2-deficient mice. Our results reveal enzymatic machinery controlling cholesterol levels through S-nitrosylation and suggest a distinct treatment paradigm for cardiovascular disease.


Assuntos
Pró-Proteína Convertase 9 , S-Nitrosotióis , Camundongos , Animais , Proteínas/metabolismo , Oxirredutases/metabolismo , S-Nitrosotióis/metabolismo , Homeostase , Óxido Nítrico/metabolismo , Proteínas de Membrana
2.
Adv Biol Regul ; 75: 100661, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31668661

RESUMO

The Golgi apparatus serves a key role in processing and sorting lipids and proteins for delivery to their final cellular destinations. Vesicle exit from the Golgi initiates with directional deformation of the lipid bilayer to produce a bulge. Several mechanisms have been described by which lipids and proteins can induce directional membrane curvature to promote vesicle budding. Here we review some of the mechanisms implicated in inducing membrane curvature at the Golgi to promote vesicular trafficking to various cellular destinations.


Assuntos
Complexo de Golgi/patologia , Bicamadas Lipídicas/metabolismo , Proteínas de Membrana/metabolismo , Humanos , Fosfatos de Fosfatidilinositol/metabolismo , Transporte Proteico/fisiologia , Vesículas Transportadoras
3.
Dev Cell ; 50(5): 573-585.e5, 2019 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-31231041

RESUMO

Vesicle budding for Golgi-to-plasma membrane trafficking is a key step in secretion. Proteins that induce curvature of the Golgi membrane are predicted to be required, by analogy to vesicle budding from other membranes. Here, we demonstrate that GOLPH3, upon binding to the phosphoinositide PI4P, induces curvature of synthetic membranes in vitro and the Golgi in cells. Moreover, efficient Golgi-to-plasma membrane trafficking critically depends on the ability of GOLPH3 to curve the Golgi membrane. Interestingly, uncoupling of GOLPH3 from its binding partner MYO18A results in extensive curvature of Golgi membranes, producing dramatic tubulation of the Golgi, but does not support forward trafficking. Thus, forward trafficking from the Golgi to the plasma membrane requires the ability of GOLPH3 both to induce Golgi membrane curvature and to recruit MYO18A. These data provide fundamental insight into the mechanism of Golgi trafficking and into the function of the unique Golgi secretory oncoproteins GOLPH3 and MYO18A.


Assuntos
Complexo de Golgi/metabolismo , Lipossomos/metabolismo , Proteínas de Membrana/metabolismo , Fosfatidilinositóis/metabolismo , Via Secretória , Células HEK293 , Células HeLa , Humanos , Membranas Intracelulares/química , Membranas Intracelulares/metabolismo , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Lipossomos/química , Proteínas de Membrana/química , Miosinas/metabolismo , Fosfatidilinositóis/química , Ligação Proteica , Domínios Proteicos
4.
Genes (Basel) ; 10(3)2019 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-30934642

RESUMO

The Golgi organelle duplicates its protein and lipid content to segregate evenly between two daughter cells after mitosis. However, how Golgi biogenesis is regulated during interphase remains largely unknown. Here we show that messenger RNA (mRNA) expression of GOLPH3 and GOLGA2, two genes encoding Golgi proteins, is induced specifically in G1 phase, suggesting a link between cell cycle regulation and Golgi growth. We have examined the role of E2F transcription factors, critical regulators of G1 to S progression of the cell cycle, in the expression of Golgi proteins during interphase. We show that promoter activity for GOLPH3, a Golgi protein that is also oncogenic, is induced by E2F1-3 and repressed by E2F7. Mutation of the E2F motifs present in the GOLPH3 promoter region abrogates E2F1-mediated induction of a GOLPH3 luciferase reporter construct. Furthermore, we identify a critical CREB/ATF element in the GOLPH3 promoter that is required for its steady state and ATF2-induced expression. Interestingly, depletion of GOLPH3 with small interfering RNA (siRNA) delays the G1 to S transition in synchronized U2OS cells. Taken together, our results reveal a link between cell cycle regulation and Golgi function, and suggest that E2F-mediated regulation of Golgi genes is required for the timely progression of the cell cycle.


Assuntos
Fator 2 Ativador da Transcrição/metabolismo , Fatores de Transcrição E2F/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/genética , Animais , Sítios de Ligação , Ciclo Celular , Linhagem Celular Tumoral , Regulação da Expressão Gênica , Complexo de Golgi/genética , Complexo de Golgi/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Camundongos , Mutação , Células NIH 3T3 , Fosfoproteínas/genética , Regiões Promotoras Genéticas
5.
J Lipid Res ; 60(4): 747-752, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30718284

RESUMO

The discovery of the phosphatidylinositol-3-kinase (PI3K) pathway was a major advance in understanding growth factor signaling. The high frequency of PI3K pathway mutations in many cancers has encouraged a new field targeting cancer driver mutations. Although there have been many successes, targeting PI3K itself has proven challenging, in part because of its multiple isoforms with distinct roles. Despite promising preclinical results, development of PI3K inhibitors as pharmacologic anticancer agents has been limited by modest single-agent efficacy and significant adverse effects. If we could overcome these limitations, PI3K inhibitors would be a powerful cancer-fighting tool. Data from phase III clinical trials yields insight into some of the problems with PI3K inhibitors. Recent advances have shed light on the mechanisms of tumor resistance to PI3K inhibitors via feedback pathways that cause elevated insulin levels that then activate the same PI3K pathways that are the targets of inhibition. Improving our understanding of the complex regulatory feedback pathways that activate in response to PI3K inhibition will reveal ways to increase the efficacy of PI3K inhibitors and reduce adverse effects, increasing the usefulness of this class as a treatment option for multiple cancer types.


Assuntos
Antineoplásicos/farmacologia , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Neoplasias/tratamento farmacológico , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Animais , Humanos , Neoplasias/metabolismo , Neoplasias/patologia
6.
J Lipid Res ; 60(2): 269-275, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30266835

RESUMO

GOLPH3 is a peripheral membrane protein localized to the Golgi and its vesicles, but its purpose had been unclear. We found that GOLPH3 binds specifically to the phosphoinositide phosphatidylinositol(4)phosphate [PtdIns(4)P], which functions at the Golgi to promote vesicle exit for trafficking to the plasma membrane. PtdIns(4)P is enriched at the trans-Golgi and so recruits GOLPH3. Here, a GOLPH3 complex is formed when it binds to myosin18A (MYO18A), which binds F-actin. This complex generates a pulling force to extract vesicles from the Golgi; interference with this GOLPH3 complex results in dramatically reduced vesicle trafficking. The GOLPH3 complex has been identified as a driver of cancer in humans, likely through multiple mechanisms that activate secretory trafficking. In this review, we summarize the literature that identifies the nature of the GOLPH3 complex and its role in cancer. We also consider the GOLPH3 complex as a hub with the potential to reveal regulation of the Golgi and suggest the possibility of GOLPH3 complex inhibition as a therapeutic approach in cancer.


Assuntos
Complexo de Golgi/metabolismo , Proteínas de Membrana/metabolismo , Neoplasias/metabolismo , Neoplasias/patologia , Fosfatos de Fosfatidilinositol/metabolismo , Animais , Transporte Biológico , Humanos
7.
J Med Chem ; 61(23): 10463-10472, 2018 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-30380865

RESUMO

Using a novel chemistry-based assay for identifying electrophilic natural products in unprocessed extracts, we identified the PI3-kinase/mTOR dual inhibitor neolymphostin A from Salinispora arenicola CNY-486. The method further showed that the vinylogous ester substituent on the neolymphostin core was the exact site for enzyme conjugation. Tandem MS/MS experiments on PI3Kα treated with the inhibitor revealed that neolymphostin covalently modified Lys802 with a shift in mass of +306 amu, corresponding to addition of the inhibitor and elimination of methanol. The binding pose of the inhibitor bound to PI3Kα was modeled, and hydrogen-deuterium exchange mass spectrometry experiments supported this model. Against a panel of kinases, neolymphostin showed good selectivity for PI3-kinase and mTOR. In addition, the natural product blocked AKT phosphorylation in live cells with an IC50 of ∼3 nM. Taken together, neolymphostin is the first reported example of a covalent kinase inhibitor from the bacterial domain of life.


Assuntos
Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Ésteres/química , Inibidores de Fosfoinositídeo-3 Quinase , Quinolinas/química , Quinolinas/farmacologia , Serina-Treonina Quinases TOR/antagonistas & inibidores , Inibidores Enzimáticos/metabolismo , Simulação de Acoplamento Molecular , Fosfatidilinositol 3-Quinases/química , Fosfatidilinositol 3-Quinases/metabolismo , Conformação Proteica , Quinolinas/metabolismo
8.
Adv Biol Regul ; 67: 84-92, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28942352

RESUMO

MYO18A is a divergent member of the myosin family characterized by the presence of an amino-terminal PDZ domain. MYO18A has been found in a few different complexes involved in intracellular transport processes. MYO18A is found in a complex with LURAP1 and MRCK that functions in retrograde treadmilling of actin. It also has been found in a complex with PAK2, ßPIX, and GIT1, functioning to transport that protein complex from focal adhesions to the leading edge. Finally, a high proportion of MYO18A is found in complex with GOLPH3 at the trans Golgi, where it functions to promote vesicle budding for Golgi-to-plasma membrane trafficking. Interestingly, MYO18A has been implicated as a cancer driver, as have other components of the GOLPH3 pathway. It remains uncertain as to whether or not MYO18A has intrinsic motor activity. While many questions remain, MYO18A is a fascinatingly unique myosin that is essential in higher organisms.


Assuntos
Membrana Celular/metabolismo , Complexo de Golgi/metabolismo , Miosinas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Transporte Biológico Ativo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Membrana Celular/genética , Complexo de Golgi/genética , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Miosinas/genética , Fatores de Troca de Nucleotídeo Guanina Rho/genética , Fatores de Troca de Nucleotídeo Guanina Rho/metabolismo , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Quinases Ativadas por p21/genética , Quinases Ativadas por p21/metabolismo
9.
J Biol Chem ; 292(34): 14308-14309, 2017 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-28842476

RESUMO

Phosphatidylserine (PtdSer) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) have been implicated in the maintenance of caveolae, but direct evidence that these lipids are required for normal caveolar structure and dynamics in living cells has been lacking. A new study by Fairn and colleagues uses sophisticated tools to perturb specific lipids in living cells to assess the consequences for caveolae. This study demonstrates disparate roles for these lipids in the stability and mobility of caveolae and points the way for future work to understand how these lipids contribute to the biology of caveolae.


Assuntos
Cavéolas/metabolismo , Membrana Celular/metabolismo , Fosfatidilinositol 4,5-Difosfato/metabolismo , Fosfatidilserinas/metabolismo , Animais , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Cavéolas/química , Caveolinas/química , Caveolinas/metabolismo , Membrana Celular/química , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/química , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Musculares/química , Proteínas Musculares/metabolismo , Proteínas de Ligação a Fosfato , Fosfatidilinositol 4,5-Difosfato/química , Fosfatidilserinas/química , Multimerização Proteica , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/metabolismo , Proteínas de Transporte Vesicular
10.
Curr Opin Cell Biol ; 45: 17-23, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28213314

RESUMO

The Golgi is generally recognized for its central role in the secretory pathway to orchestrate protein post-translational modification and trafficking of proteins and lipids to their final destination. Despite the common view of the Golgi as an inert sorting organelle, emerging data demonstrate that important signaling events occur at the Golgi, including those that regulate the trafficking function of the Golgi. The phosphatidylinositol-4-phosphate/GOLPH3/MYO18A/F-actin complex serves as a hub for signals that regulate Golgi trafficking function. Furthermore, the Golgi is increasingly appreciated for its important role in cell growth and in driving oncogenic transformation, as illuminated by the discovery that GOLPH3 and MYO18A are cancer drivers.


Assuntos
Complexo de Golgi/metabolismo , Metabolismo dos Lipídeos , Transporte Proteico , Transdução de Sinais , Animais , Proliferação de Células , Transformação Celular Neoplásica/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Processamento de Proteína Pós-Traducional
11.
Mol Biol Cell ; 27(24): 3828-3840, 2016 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-27708138

RESUMO

The mechanism of directional cell migration remains an important problem, with relevance to cancer invasion and metastasis. GOLPH3 is a common oncogenic driver of human cancers, and is the first oncogene that functions at the Golgi in trafficking to the plasma membrane. Overexpression of GOLPH3 is reported to drive enhanced cell migration. Here we show that the phosphatidylinositol-4-phosphate/GOLPH3/myosin 18A/F-actin pathway that is critical for Golgi-to-plasma membrane trafficking is necessary and limiting for directional cell migration. By linking the Golgi to the actin cytoskeleton, GOLPH3 promotes reorientation of the Golgi toward the leading edge. GOLPH3 also promotes reorientation of lysosomes (but not other organelles) toward the leading edge. However, lysosome function is dispensable for migration and the GOLPH3 dependence of lysosome movement is indirect, via GOLPH3's effect on the Golgi. By driving reorientation of the Golgi to the leading edge and driving forward trafficking, particularly to the leading edge, overexpression of GOLPH3 drives trafficking to the leading edge of the cell, which is functionally important for directional cell migration. Our identification of a novel pathway for Golgi reorientation controlled by GOLPH3 provides new insight into the mechanism of directional cell migration with important implications for understanding GOLPH3's role in cancer.


Assuntos
Complexo de Golgi/metabolismo , Proteínas de Membrana/metabolismo , Actinas/metabolismo , Sequência de Aminoácidos , Técnicas de Cultura de Células , Membrana Celular/metabolismo , Movimento Celular/fisiologia , Polaridade Celular , Citoesqueleto , Células HeLa , Humanos , Proteínas de Membrana/fisiologia , Miosinas/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Transporte Proteico/fisiologia , Transdução de Sinais
12.
Front Neurosci ; 9: 362, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26500484

RESUMO

The Golgi protein GOLPH3 binds to PtdIns(4)P and MYO18A, linking the Golgi to the actin cytoskeleton. The GOLPH3 pathway is essential for vesicular trafficking from the Golgi to the plasma membrane. A side effect of GOLPH3-dependent trafficking is to generate the extended ribbon shape of the Golgi. Perturbation of the pathway results in changes to both Golgi morphology and secretion, with functional consequences for the cell. The cellular response to DNA damage provides an example of GOLPH3-mediated regulation of the Golgi. Upon DNA damage, DNA-PK phosphorylation of GOLPH3 increases binding to MYO18A, activating the GOLPH3 pathway, which consequently results in Golgi fragmentation, reduced trafficking, and enhanced cell survival. The PtdIns(4)P/GOLPH3/MYO18A/F-actin pathway provides new insight into the relationship between Golgi morphology and function, and their regulation.

13.
Nat Genet ; 47(5): 528-34, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25848753

RESUMO

Pediatric-onset ataxias often present clinically as developmental delay and intellectual disability, with prominent cerebellar atrophy as a key neuroradiographic finding. Here we describe a new clinically distinguishable recessive syndrome in 12 families with cerebellar atrophy together with ataxia, coarsened facial features and intellectual disability, due to truncating mutations in the sorting nexin gene SNX14, encoding a ubiquitously expressed modular PX domain-containing sorting factor. We found SNX14 localized to lysosomes and associated with phosphatidylinositol (3,5)-bisphosphate, a key component of late endosomes/lysosomes. Patient-derived cells showed engorged lysosomes and a slower autophagosome clearance rate upon autophagy induction by starvation. Zebrafish morphants for snx14 showed dramatic loss of cerebellar parenchyma, accumulation of autophagosomes and activation of apoptosis. Our results characterize a unique ataxia syndrome due to biallelic SNX14 mutations leading to lysosome-autophagosome dysfunction.


Assuntos
Doenças Cerebelares/genética , Cerebelo/patologia , Lisossomos/metabolismo , Fagossomos/metabolismo , Nexinas de Classificação/genética , Ataxias Espinocerebelares/genética , Animais , Atrofia/genética , Autofagia , Pré-Escolar , Feminino , Frequência do Gene , Humanos , Lactente , Escore Lod , Doenças por Armazenamento dos Lisossomos/genética , Masculino , Mutação , Síndrome , Peixe-Zebra
14.
Cancer Res ; 75(4): 624-7, 2015 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-25634214

RESUMO

GOLPH3 is the first example of an oncogene that functions in secretory trafficking at the Golgi. The discovery of GOLPH3's roles in both cancer and Golgi trafficking raises questions about how GOLPH3 and the Golgi contribute to cancer. Our recent investigation of the regulation of GOLPH3 revealed a surprising response by the Golgi upon DNA damage that is mediated by DNA-PK and GOLPH3. These results provide new insight into the DNA damage response with important implications for understanding the cellular response to standard cancer therapeutic agents.


Assuntos
Dano ao DNA/genética , Proteína Quinase Ativada por DNA/genética , Proteínas de Membrana/genética , Neoplasias/genética , Movimento Celular/genética , Complexo de Golgi/genética , Complexo de Golgi/metabolismo , Humanos , Neoplasias/patologia , Transporte Proteico/genética , Transdução de Sinais/genética
15.
Cell ; 156(3): 413-27, 2014 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-24485452

RESUMO

The response to DNA damage, which regulates nuclear processes such as DNA repair, transcription, and cell cycle, has been studied thoroughly. However, the cytoplasmic response to DNA damage is poorly understood. Here, we demonstrate that DNA damage triggers dramatic reorganization of the Golgi, resulting in its dispersal throughout the cytoplasm. We further show that DNA-damage-induced Golgi dispersal requires GOLPH3/MYO18A/F-actin and the DNA damage protein kinase, DNA-PK. In response to DNA damage, DNA-PK phosphorylates GOLPH3, resulting in increased interaction with MYO18A, which applies a tensile force to the Golgi. Interference with the Golgi DNA damage response by depletion of DNA-PK, GOLPH3, or MYO18A reduces survival after DNA damage, whereas overexpression of GOLPH3, as is observed frequently in human cancers, confers resistance to killing by DNA-damaging agents. Identification of the DNA-damage-induced Golgi response reveals an unexpected pathway through DNA-PK, GOLPH3, and MYO18A that regulates cell survival following DNA damage.


Assuntos
Dano ao DNA , Proteína Quinase Ativada por DNA/metabolismo , Complexo de Golgi/metabolismo , Proteínas de Membrana/metabolismo , Miosinas/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , Sobrevivência Celular , Células Cultivadas , Humanos , Proteínas de Membrana/química , Camundongos , Dados de Sequência Molecular , Fosforilação , Ratos , Alinhamento de Sequência
16.
Mol Biol Cell ; 24(6): 796-808, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23345592

RESUMO

GOLPH3 is a phosphatidylinositol-4-phosphate (PI4P) effector that plays an important role in maintaining Golgi architecture and anterograde trafficking. GOLPH3 does so through its ability to link trans-Golgi membranes to F-actin via its interaction with myosin 18A (MYO18A). GOLPH3 also is known to be an oncogene commonly amplified in human cancers. GOLPH3L is a GOLPH3 paralogue found in all vertebrate genomes, although previously it was largely uncharacterized. Here we demonstrate that although GOLPH3 is ubiquitously expressed in mammalian cells, GOLPH3L is present in only a subset of tissues and cell types, particularly secretory tissues. We show that, like GOLPH3, GOLPH3L binds to PI4P, localizes to the Golgi as a consequence of its PI4P binding, and is required for efficient anterograde trafficking. Surprisingly, however, we find that perturbations of GOLPH3L expression produce effects on Golgi morphology that are opposite to those of GOLPH3 and MYO18A. GOLPH3L differs critically from GOLPH3 in that it is largely unable to bind to MYO18A. Our data demonstrate that despite their similarities, unexpectedly, GOLPH3L antagonizes GOLPH3/MYO18A at the Golgi.


Assuntos
Complexo de Golgi/ultraestrutura , Proteínas de Membrana/metabolismo , Miosinas/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Fosfoproteínas/metabolismo , Células 3T3 , Sequência de Aminoácidos , Animais , Linhagem Celular , Glicosiltransferases/metabolismo , Complexo de Golgi/metabolismo , Células HEK293 , Células HeLa , Humanos , Células MCF-7 , Proteínas de Membrana/genética , Camundongos , Miosinas/genética , Transporte Proteico , Interferência de RNA , RNA Interferente Pequeno , Alinhamento de Sequência , Transdução de Sinais
17.
Dev Biol ; 372(1): 17-27, 2012 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-23000359

RESUMO

The Drosophila RhoGEF Pebble (Pbl) is required for cytokinesis and migration of mesodermal cells. In a screen for genes that could suppress migration defects in pbl mutants we identified the phosphatidylinositol phosphate (PtdInsP) regulator pi5k59B. Genetic interaction tests with other PtdInsP regulators suggested that PtdIns(4,5)P2 levels are important for mesoderm migration when Pbl is depleted. Consistent with this, the leading front of migrating mesodermal cells was enriched for PtdIns(4,5)P2. Given that Pbl contains a Pleckstrin Homology (PH) domain, a known PtdInsP-binding motif, we examined PtdInsP-binding of Pbl and the importance of the PH domain for Pbl function. In vitro lipid blot assays showed that Pbl binds promiscuously to PtdInsPs, with binding strength associated with the degree of phosphorylation. Pbl was also able to bind lipid vesicles containing PtdIns(4,5)P2 but binding was strongly reduced upon deletion of the PH domain. Similarly, in vivo, loss of the PH domain prevented localisation of Pbl to the cell cortex and severely affected several aspects of early mesoderm development, including flattening of the invaginated tube onto the ectoderm, extension of protrusions, and dorsal migration to form a monolayer. Pbl lacking the PH domain could still localise to the cytokinetic furrow, however, and cytokinesis failure was reduced in pbl(ΔPH) mutants. Taken together, our results support a model in which interaction of the PH-domain of Pbl with PtdIns(4,5)P2 helps localise it to the plasma membrane which is important for mesoderm migration.


Assuntos
Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Fatores de Troca do Nucleotídeo Guanina/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Mesoderma/metabolismo , Animais , Sítios de Ligação , Membrana Celular/metabolismo , Movimento Celular , Drosophila/genética , Drosophila/metabolismo , Guanosina Trifosfato/metabolismo , Fosfatidilinositol 4,5-Difosfato/metabolismo , Fosfatidilinositóis/metabolismo , Fosforilação , Estrutura Terciária de Proteína , Transdução de Sinais
18.
J Biol Chem ; 287(33): 27637-47, 2012 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-22745132

RESUMO

Hepatitis C virus (HCV) RNA replicates within the ribonucleoprotein complex, assembled on the endoplasmic reticulum (ER)-derived membranous structures closely juxtaposed to the lipid droplets that facilitate the post-replicative events of virion assembly and maturation. It is widely believed that the assembled virions piggy-back onto the very low density lipoprotein particles for secretion. Lipid phosphoinositides are important modulators of intracellular trafficking. Golgi-localized phosphatidylinositol 4-phosphate (PI4P) recruits proteins involved in Golgi trafficking to the Golgi membrane and promotes anterograde transport of secretory proteins. Here, we sought to investigate the role of Golgi-localized PI4P in the HCV secretion process. Depletion of the Golgi-specific PI4P pool by Golgi-targeted PI4P phosphatase hSac1 K2A led to significant reduction in HCV secretion without any effect on replication. We then examined the functional role of a newly identified PI4P binding protein GOLPH3 in the viral secretion process. GOLPH3 is shown to maintain a tensile force on the Golgi, required for vesicle budding via its interaction with an unconventional myosin, MYO18A. Silencing GOLPH3 led to a dramatic reduction in HCV virion secretion, as did the silencing of MYO18A. The reduction in virion secretion was accompanied by a concomitant accumulation of intracellular virions, suggesting a stall in virion egress. HCV-infected cells displayed a fragmented and dispersed Golgi pattern, implicating involvement in virion morphogenesis. These studies establish the role of PI4P and its interacting protein GOLPH3 in HCV secretion and strengthen the significance of the Golgi secretory pathway in this process.


Assuntos
Complexo de Golgi/metabolismo , Hepacivirus/metabolismo , Hepatite C/metabolismo , Proteínas de Membrana/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Liberação de Vírus/fisiologia , Transporte Biológico Ativo/genética , Linhagem Celular Tumoral , Complexo de Golgi/genética , Complexo de Golgi/virologia , Hepacivirus/genética , Hepatite C/genética , Humanos , Membranas Intracelulares/metabolismo , Membranas Intracelulares/virologia , Proteínas de Membrana/genética , Miosinas/genética , Miosinas/metabolismo , Fosfatos de Fosfatidilinositol/genética , Vírion/genética , Vírion/metabolismo
19.
Cancer Cell ; 19(6): 715-27, 2011 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-21665146

RESUMO

Tumor inflammation promotes angiogenesis, immunosuppression, and tumor growth, but the mechanisms controlling inflammatory cell recruitment to tumors are not well understood. We found that a range of chemoattractants activating G protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs) and Toll-like/IL-1 receptors (TLR/IL1Rs) unexpectedly initiate tumor inflammation by activating the PI3-kinase isoform p110γ in Gr1+CD11b+ myeloid cells. Whereas GPCRs activate p110γ in a Ras/p101-dependent manner, RTKs and TLR/IL1Rs directly activate p110γ in a Ras/p87-dependent manner. Once activated, p110γ promotes inside-out activation of a single integrin, α4ß1, causing myeloid cell invasion into tumors. Pharmacological or genetic blockade of p110γ suppressed inflammation, growth, and metastasis of implanted and spontaneous tumors, revealing an important therapeutic target in oncology.


Assuntos
Classe Ib de Fosfatidilinositol 3-Quinase/fisiologia , Inflamação/etiologia , Neoplasias/patologia , Receptores Proteína Tirosina Quinases/fisiologia , Receptores de Interleucina-1/fisiologia , Receptores Toll-Like/fisiologia , Animais , Adesão Celular , Movimento Celular , Progressão da Doença , Humanos , Integrina alfa4beta1/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Metástase Neoplásica , Neoplasias/prevenção & controle , Proteínas ras/fisiologia
20.
Mol Biol Cell ; 21(13): 2327-37, 2010 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-20444975

RESUMO

Protein kinase D (PKD) plays a critical role at the trans-Golgi network by regulating the fission of transport carriers destined for the plasma membrane. Two known Golgi-localized PKD substrates, PI4-kinase IIIbeta and the ceramide transfer protein CERT, mediate PKD signaling to influence vesicle trafficking to the plasma membrane and sphingomyelin synthesis, respectively. PKD is recruited and activated at the Golgi through interaction with diacylglycerol, a pool of which is generated as a by-product of sphingomyelin synthesis from ceramide. Here we identify a novel substrate of PKD at the Golgi, the oxysterol-binding protein OSBP. Using a substrate-directed phospho-specific antibody that recognizes the optimal PKD consensus motif, we show that PKD phosphorylates OSBP at Ser240 in vitro and in cells. We further show that OSBP phosphorylation occurs at the Golgi. Phosphorylation of OSBP by PKD does not modulate dimerization, sterol binding, or affinity for PI(4)P. Instead, phosphorylation attenuates OSBP Golgi localization in response to 25-hydroxycholesterol and cholesterol depletion, impairs CERT Golgi localization, and promotes Golgi fragmentation.


Assuntos
Complexo de Golgi/metabolismo , Proteína Quinase C/metabolismo , Receptores de Esteroides/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , Humanos , Dados de Sequência Molecular , Fosforilação , Proteína Quinase C/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Receptores de Esteroides/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Alinhamento de Sequência , Serina/metabolismo
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