scholarly journals The effector TepP mediates the recruitment and activation of Phosphoinositide 3 Kinase on early Chlamydia trachomatis vacuoles

2017 ◽  
Author(s):  
Victoria Carpenter ◽  
Yi-Shan Chen ◽  
Lee Dolat ◽  
Raphael H. Valdivia
Keyword(s):  
Chlamydia Trachomatis ◽  
Epithelial Cells ◽  
Membrane Trafficking ◽  
Adaptor Protein ◽  
Membrane Dynamics ◽  
Effector Proteins ◽  
Type I ◽  
Type I Ifn ◽  
Bacterial Replication ◽  
Phosphoinositide 3 Kinase

ABSTRACTChlamydia trachomatis delivers multiple Type 3 secreted effector proteins to host epithelial cells to manipulate cytoskeletal functions, membrane dynamics and signaling pathways. TepP is the most abundant effector protein secreted early in infection but its molecular function is poorly understood. In this report, we provide evidence that TepP is important for bacterial replication in cervical epithelial cells, the activation of Type I IFN genes, and the recruitment of Class I phosphoinositide 3 kinases (PI3K) and the signaling adaptor protein CrkL to nascent pathogen-containing vacuoles (inclusions). We also show that TepP is a target of tyrosine phosphorylation by Src kinases but these modifications do not appear to influence the recruitment of PI3K or CrkL. The translocation of TepP correlated with an increase in the intracellular pools of phosphoinositide 3,4,5 triphosphate but not the activation of the pro-survival kinase Akt, suggesting that TepP-mediated activation of PI3K is spatially restricted to early inclusions. Furthermore, we linked PI3K activity to the dampening of transcription of Type I IFN induced genes early in infection. Overall, these findings indicate that TepP can modulate cell signaling and potentially membrane trafficking events by spatially restricted activation of PI3K.

scholarly journals The Effector TepP Mediates Recruitment and Activation of Phosphoinositide 3-Kinase on Early Chlamydia trachomatis Vacuoles

mSphere ◽  
2017 ◽  
Vol 2 (4) ◽  
Author(s):  
Victoria Carpenter ◽  
Yi-Shan Chen ◽  
Lee Dolat ◽  
Raphael H. Valdivia
Keyword(s):  
Chlamydia Trachomatis ◽  
Epithelial Cells ◽  
Immune Responses ◽  
Cell Survival ◽  
Host Cell ◽  
Adaptor Protein ◽  
Membrane Dynamics ◽  
Scaffolding Protein ◽  
Type I ◽  
Internal Membrane

ABSTRACT This article shows that chlamydia recruit PI3K, an enzyme important for host cell survival and internal membrane functions, to the pathogens inside cells by secreting a scaffolding protein called TepP. TepP enhances Chlamydia replication and dampens the activation of immune responses. Chlamydia trachomatis delivers multiple type 3 secreted effector proteins to host epithelial cells to manipulate cytoskeletal functions, membrane dynamics, and signaling pathways. TepP is the most abundant effector protein secreted early in infection, but its molecular function is poorly understood. In this report, we provide evidence that TepP is important for bacterial replication in cervical epithelial cells, activation of type I IFN genes, and recruitment of class I phosphoinositide 3-kinases (PI3K) and signaling adaptor protein CrkL to nascent pathogen-containing vacuoles (inclusions). We also show that TepP is a target of tyrosine phosphorylation by Src kinases but that these modifications do not appear to influence the recruitment of PI3K or CrkL. The translocation of TepP correlated with an increase in the intracellular pools of phosphoinositide-(3,4,5)-triphosphate but not the activation of the prosurvival kinase Akt, suggesting that TepP-mediated activation of PI3K is spatially restricted to early inclusions. Furthermore, we linked PI3K activity to the dampening of transcription of type I interferon (IFN)-induced genes early in infection. Overall, these findings indicate that TepP can modulate cell signaling and, potentially, membrane trafficking events by spatially restricted activation of PI3K. IMPORTANCE This article shows that Chlamydia recruits PI3K, an enzyme important for host cell survival and internal membrane functions, to the pathogens inside cells by secreting a scaffolding protein called TepP. TepP enhances Chlamydia replication and dampens the activation of immune responses.

scholarly journals Distinct Roles for the Yeast Phosphatidylinositol 4-Kinases, Stt4p and Pik1p, in Secretion, Cell Growth, and Organelle Membrane Dynamics

2000 ◽  
Vol 11 (8) ◽  
pp. 2673-2689 ◽  
Author(s):  
Anjon Audhya ◽  
Michelangelo Foti ◽  
Scott D. Emr
Keyword(s):  
Cell Growth ◽  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Membrane Dynamics ◽  
Small Gtpase ◽  
Effector Proteins ◽  
Restrictive Temperature ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoskeleton Organization ◽  
Yeast Viability

The yeast Saccharomyces cerevisiae possesses two genes that encode phosphatidylinositol (PtdIns) 4-kinases,STT4 and PIK1. Both gene products phosphorylate PtdIns at the D-4 position of the inositol ring to generate PtdIns(4)P, which plays an essential role in yeast viability because deletion of either STT4 orPIK1 is lethal. Furthermore, although both enzymes have the same biochemical activity, increased expression of either kinase cannot compensate for the loss of the other, suggesting that these kinases regulate distinct intracellular functions, each of which is required for yeast cell growth. By the construction of temperature-conditional single and double mutants, we have found that Stt4p activity is required for the maintenance of vacuole morphology, cell wall integrity, and actin cytoskeleton organization. In contrast, Pik1p is essential for normal secretion, Golgi and vacuole membrane dynamics, and endocytosis. Strikingly,pik1tscells exhibit a rapid defect in secretion of Golgi-modified secretory pathway cargos, Hsp150p and invertase, whereas stt4tscells exhibit no detectable secretory defects. Both single mutants reduce PtdIns(4)P by ∼50%; however,stt4ts/pik1tsdouble mutant cells produce more than 10-fold less PtdIns(4)P as well as PtdIns(4,5)P2. The aberrant Golgi morphology found in pik1tsmutants is strikingly similar to that found in cells lacking the function of Arf1p, a small GTPase that is known to regulate multiple membrane trafficking events throughout the cell. Consistent with this observation, arf1 mutants exhibit reduced PtdIns(4)P levels. In contrast, diminished levels of PtdIns(4)P observed in stt4tscells at restrictive temperature result in a dramatic change in vacuole size compared with pik1tscells and persistent actin delocalization. Based on these results, we propose that Stt4p and Pik1p act as the major, if not the only, PtdIns 4-kinases in yeast and produce distinct pools of PtdIns(4)P and PtdIns(4,5)P2that act on different intracellular membranes to recruit or activate as yet uncharacterized effector proteins.

scholarly journals HIV blocks Type I IFN signaling through disruption of STAT1 phosphorylation

2018 ◽  
Vol 24 (8) ◽  
pp. 490-500 ◽  
Author(s):  
Nam V Nguyen ◽  
James T Tran ◽  
David Jesse Sanchez
Keyword(s):  
Gene Expression ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Type I ◽  
Type I Ifn ◽  
Antiviral State ◽  
Receptor Signaling Pathway ◽  
Multiple Signaling ◽  
Inducible Gene ◽  
Stat Pathway

This study investigates the modulation of Type I IFN induction of an antiviral state by HIV. IFNs, including IFN-α, are key innate immune cytokines that activate the JAK/STAT pathway leading to the expression of IFN-stimulated genes. IFN-stimulated gene expression establishes the antiviral state, limiting viral infection in IFN-α-stimulated microenvironments. Our previous studies have shown that HIV proteins disrupt the induction of IFN-α by degradation of IFN-β promoter stimulator-1, an adaptor protein for the up-regulation and release of IFN-α into the local microenvironment via the retinoic acid-inducible gene 1-like receptor signaling pathway. However, IFN-α is still released from other sources such as plasmacytoid dendritic cells via TLR-dependent recognition of HIV. Here we report that the activation of the JAK/STAT pathway by IFN-α stimulation is disrupted by HIV proteins Vpu and Nef, which both reduce IFN-α induction of STAT1 phosphorylation. Thus, HIV would still be able to avoid antiviral protection induced by IFN-α in the local microenvironment. These findings show that HIV blocks multiple signaling points that would lead to the up-regulation of IFN-stimulated genes, allowing more effective replication in IFN-α-rich environments.

scholarly journals Salmonella-Containing Vacuoles Display Centrifugal Movement Associated with Cell-to-Cell Transfer in Epithelial Cells

2008 ◽  
Vol 77 (3) ◽  
pp. 996-1007 ◽  
Author(s):  
Jason Szeto ◽  
Anton Namolovan ◽  
Suzanne E. Osborne ◽  
Brian K. Coombes ◽  
John H. Brumell
Keyword(s):  
Epithelial Cells ◽  
Host Cell ◽  
Effector Proteins ◽  
Cell Periphery ◽  
Secretion Systems ◽  
T3ss Effector ◽  
Type Iii Secretion Systems ◽  
Serovar Typhimurium ◽  
Bacterial Replication ◽  
Bacterial Protein Synthesis

ABSTRACT Intracellular Salmonella enterica serovar Typhimurium (serovar Typhimurium) occupies a Salmonella-containing vacuole (SCV) where bacterial effector proteins are secreted into the host cell using type III secretion systems (T3SS). Cytoskeletal motor proteins and T3SS-delivered effector proteins facilitate SCV positioning to juxtanuclear positions where bacterial replication occurs. Here, we show that this characteristic SCV positioning is not maintained by all SCVs during infection of HeLa cells. Notably, juxtanuclear SCV localization that occurs by 8 to 14 h postinfection is followed by significant centrifugal displacement of a subset of SCVs toward the host cell periphery by 24 h postinfection. This novel phenotype requires bacterial protein synthesis, a functional Salmonella pathogenicity island 2 (SPI-2)-encoded T3SS, intact microtubules, and kinesin-1 motor protein. Bacteria lacking PipB2, a kinesin-recruiting T3SS effector, did not exhibit centrifugal displacement and remained at juxtanuclear positions throughout 24 h of infection. While levels of the SPI-2 effectors PipB2 and SifA increased during 24 h postinfection, a corresponding decrease in levels of the SPI-1 T3SS effectors SipA and SopB, both known to mediate juxtanuclear SCV positioning, was observed. A fluorescence-based assay indicated that wild-type serovar Typhimurium transferred from infected to uninfected epithelial cells while strains deficient in SPI-2 T3SS secretion or PipB2 did not. Our results reveal a novel SCV phenotype implicated in the cell-to-cell spread of serovar Typhimurium during infection.

Hyposmotic activation of ICl,swell in rabbit nonpigmented ciliary epithelial cells involves increased ClC-3 trafficking to the plasma membrane

2004 ◽  
Vol 82 (6) ◽  
pp. 708-718 ◽  
Author(s):  
John P Vessey ◽  
Chanjuan Shi ◽  
Christine AB Jollimore ◽  
Kelly T Stevens ◽  
Miguel Coca-Prados ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Kinase Inhibitor ◽  
Regulatory Volume Decrease ◽  
Membrane Dynamics ◽  
Cell Swelling ◽  
Cl Channels ◽  
Phosphoinositide 3 Kinase ◽  
Nonpigmented Ciliary Epithelial ◽  
Volume Decrease

In mammalian nonpigmented ciliary epithelial (NPE) cells, hyposmotic stimulation leading to cell swelling activates an outwardly rectifying Cl– conductance (ICl,swell), which, in turn, results in regulatory volume decrease. The aim of this study was to determine whether increased trafficking of intracellular ClC-3 Cl channels to the plasma membrane could contribute to the ICl,swell following hyposmotic stimulation. Our results demonstrate that hyposmotic stimulation reversibly activates an outwardly rectifying Cl– current that is inhibited by phorbol-12-dibutyrate and niflumic acid. Transfection with ClC-3 antisense, but not sense, oligonucleotides reduced ClC-3 expression as well as ICl,swell. Intracellular dialysis with 2 different ClC-3 antibodies abolished activation of ICl,swell. Immunofluorescence microscopy showed that hyposmotic stimulation increased ClC-3 immunoreactivity at the plasma membrane. To determine whether this increased expression of ClC-3 at the plasma membrane could be due to increased vesicular trafficking, we examined membrane dynamics with the fluorescent membrane dye FM1-43. Hyposmotic stimulation rapidly increased the rate of exocytosis, which, along with ICl,swell, was inhibited by the phosphoinositide-3-kinase inhibitor wortmannin and the microtubule disrupting agent, nocodazole. These findings suggest that ClC-3 channels contribute to ICl,swell following hyposmotic stimulation through increased trafficking of channels to the plasma membrane.Key words: ClC-3, NPE, cell swelling, membrane trafficking, ciliary body epithelium.

scholarly journals A host cell long noncoding RNA NR_033736 regulates type I interferon-mediated gene transcription and modulates intestinal epithelial anti-Cryptosporidium defense

2021 ◽  
Vol 17 (1) ◽  
pp. e1009241
Author(s):  
Juan Li ◽  
Kehua Jin ◽  
Min Li ◽  
Nicholas W. Mathy ◽  
Ai-Yu Gong ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Host Cell ◽  
Gene Transcription ◽  
Intestinal Epithelial Cells ◽  
Immune Defense ◽  
Fine Tuning ◽  
Type I ◽  
Intestinal Epithelial ◽  
Type I Ifn ◽  
Innate Defense

The gastrointestinal epithelium guides the immune system to differentiate between commensal and pathogenic microbiota, which relies on intimate links with the type I IFN signal pathway. Epithelial cells along the epithelium provide the front line of host defense against pathogen infection in the gastrointestinal tract. Increasing evidence supports the regulatory potential of long noncoding RNAs (lncRNAs) in immune defense but their role in regulating intestinal epithelial antimicrobial responses is still unclear. Cryptosporidium, a protozoan parasite that infects intestinal epithelial cells, is an important opportunistic pathogen in AIDS patients and a common cause of diarrhea in young children in developing countries. Recent advances in Cryptosporidium research have revealed a strong type I IFN response in infected intestinal epithelial cells. We previously identified a panel of host cell lncRNAs that are upregulated in murine intestinal epithelial cells following microbial challenge. One of these lncRNAs, NR_033736, is upregulated in intestinal epithelial cells following Cryptosporidium infection and displays a significant suppressive effect on type I IFN-controlled gene transcription in infected host cells. NR_033736 can be assembled into the ISGF3 complex and suppresses type I IFN-mediated gene transcription. Interestingly, upregulation of NR_033736 itself is triggered by the type I IFN signaling. Moreover, NR_033736 modulates epithelial anti-Cryptosporidium defense. Our data suggest that upregulation of NR_033736 provides negative feedback regulation of type I IFN signaling through suppression of type I IFN-controlled gene transcription, and consequently, contributing to fine-tuning of epithelial innate defense against microbial infection.

scholarly journals Siglec-H is an IPC-specific receptor that modulates type I IFN secretion through DAP12

Blood ◽  
2006 ◽  
Vol 107 (6) ◽  
pp. 2474-2476 ◽  
Author(s):  
Amanda L. Blasius ◽  
Marina Cella ◽  
Jorge Maldonado ◽  
Toshiyuki Takai ◽  
Marco Colonna
Keyword(s):  
Adaptor Protein ◽  
Type I ◽  
Type I Ifn ◽  
Toll Like Receptor ◽  
Cell Type ◽  
Specific Receptor ◽  
Cellular Activation ◽  
Sialic Acid Binding ◽  
Primary Cell Type ◽  
Stimulation Of

Abstract Natural interferon (IFN)-producing cells are the primary cell type responsible for production of type I IFN in response to viruses. Herein we report the identification of the first molecular marker of mouse natural interferon-producing cells (IPCs), a novel member of the sialic acid-binding immunoglobulin (Ig)-like lectin (Siglec) family termed Siglec-H. Siglec-H is expressed exclusively on IPCs and is unique among Siglec proteins in that it associates with the adaptor protein DAP12. Moreover, we show that DAP12 modulates the type I IFN response of IPCs to a Toll-like receptor 9 (TLR9) agonist. This observation explains our previous finding that stimulation of IPCs with 440c, a Siglec-H-specific antibody, reduces IPC secretion of type I IFN. Moreover, it supports a model in which engagement of DNAX-activation protein 12 (DAP12)-associated receptors with antibodies or low avidity endogenous ligands interferes with TLR-mediated cellular activation. (Blood. 2006;107:2474-2476)

Cellular functions of phosphatidylinositol 3-phosphate and FYVE domain proteins

2001 ◽  
Vol 355 (2) ◽  
pp. 249-258 ◽  
Author(s):  
David J. GILLOOLY ◽  
Anne SIMONSEN ◽  
Harald STENMARK
Keyword(s):  
Membrane Trafficking ◽  
Structural Information ◽  
Effector Proteins ◽  
Endocytic Pathway ◽  
Yeast Cells ◽  
Cellular Functions ◽  
Receptor Signalling ◽  
Fyve Domain ◽  
Cytoskeletal Regulation ◽  
Phosphoinositide 3 Kinase

PtdIns3P is a phosphoinositide 3-kinase product that has been strongly implicated in regulating membrane trafficking in both mammalian and yeast cells. PtdIns3P has been shown to be specifically located on membranes associated with the endocytic pathway. Proteins that contain FYVE zinc-finger domains are recruited to PtdIns3P-containing membranes. Structural information is now available concerning the interaction between FYVE domains and PtdIns3P. A number of proteins have been identified which contain a FYVE domain, and in this review we discuss the functions of PtdIns3P and its FYVE-domain-containing effector proteins in membrane trafficking, cytoskeletal regulation and receptor signalling.

scholarly journals Evidence for Apical Endocytosis in Polarized Hepatic Cells: Phosphoinositide 3-Kinase Inhibitors Lead to the Lysosomal Accumulation of Resident Apical Plasma Membrane Proteins

1999 ◽  
Vol 145 (5) ◽  
pp. 1089-1102 ◽  
Author(s):  
Pamela L. Tuma ◽  
Catherine M. Finnegan ◽  
Ji-Hyun Yi ◽  
Ann L. Hubbard
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Epithelial Cells ◽  
Kinase Inhibitors ◽  
Apical Membrane ◽  
Membrane Dynamics ◽  
Endocytic Pathway ◽  
Apical Plasma Membrane ◽  
Plasma Membrane Proteins ◽  
Phosphoinositide 3 Kinase

The architectural complexity of the hepatocyte canalicular surface has prevented examination of apical membrane dynamics with methods used for other epithelial cells. By adopting a pharmacological approach, we have documented for the first time the internalization of membrane proteins from the hepatic apical surface. Treatment of hepatocytes or WIF-B cells with phosphoinositide 3-kinase inhibitors, wortmannin or LY294002, led to accumulation of the apical plasma membrane proteins, 5′-nucleotidase and aminopeptidase N in lysosomal vacuoles. By monitoring the trafficking of antibody-labeled molecules, we determined that the apical proteins in vacuoles came from the apical plasma membrane. Neither newly synthesized nor transcytosing apical proteins accumulated in vacuoles. In wortmannin-treated cells, transcytosing apical proteins traversed the subapical compartment (SAC), suggesting that this intermediate in the basolateral-to-apical transcytotic pathway remained functional. Ultrastructural analysis confirmed these results. However, apically internalized proteins did not travel through SAC en route to lysosomal vacuoles, indicating that SAC is not an intermediate in the apical endocytic pathway. Basolateral membrane protein distributions did not change in treated cells, uncovering another difference in endocytosis from the two domains. Similar effects were observed in polarized MDCK cells, suggesting conserved patterns of phosphoinositide 3-kinase regulation among epithelial cells. These results confirm a long-held but unproven assumption that lysosomes are the final destination of apical membrane proteins in hepatocytes. Significantly, they also confirm our hypothesis that SAC is not an apical endosome.

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