scholarly journals The Salmonella Effector PipB2 Affects Late Endosome/Lysosome Distribution to Mediate Sif Extension

2005 ◽  
Vol 16 (9) ◽  
pp. 4108-4123 ◽  
Author(s):  
Leigh A. Knodler ◽  
Olivia Steele-Mortimer
Keyword(s):  
Host Cell ◽  
Mammalian Cells ◽  
Ectopic Expression ◽  
Bacterial Pathogen ◽  
Sequence Divergence ◽  
Cell Periphery ◽  
Host Cell Proteins ◽  
Late Endosomes ◽  
Membrane Bound ◽  
Endocytic Compartments

After internalization into mammalian cells, the bacterial pathogen Salmonella enterica resides within a membrane-bound compartment, the Salmonella-containing vacuole (SCV). During its maturation process, the SCV interacts extensively with host cell endocytic compartments, especially late endosomes/lysosomes (LE/Lys) at later stages. These interactions are mediated by the activities of multiple bacterial and host cell proteins. Here, we show that the Salmonella type III effector PipB2 reorganizes LE/Lys compartments in mammalian cells. This activity results in the centrifugal extension of lysosomal glycoprotein-rich membrane tubules, known as Salmonella-induced filaments, away from the SCV along microtubules. Salmonella overexpressing pipB2 induce the peripheral accumulation of LE/Lys compartments, reducing the frequency of LE/Lys tubulation. Furthermore, ectopic expression of pipB2 redistributes LE/Lys, but not other cellular organelles, to the cell periphery. In coexpression studies, PipB2 can overcome the effects of dominant-active Rab7 or Rab34 on LE/Lys positioning. Deletion of a C-terminal pentapeptide motif of PipB2, LFNEF, prevents its peripheral targeting and effect on organelle positioning. The PipB2 homologue PipB does not possess this motif or the same biological activity as PipB2. Therefore, it seems that a divergence in the biological functions of these two effectors can be accounted for by sequence divergence in their C termini.

scholarly journals Sustained Activation of Akt and Erk1/2 Is Required for Coxiella burnetii Antiapoptotic Activity

2008 ◽  
Vol 77 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Daniel E. Voth ◽  
Robert A. Heinzen
Keyword(s):  
Host Cell ◽  
Coxiella Burnetii ◽  
Stress Responses ◽  
Mammalian Cells ◽  
Apoptotic Cell ◽  
Parasitophorous Vacuole ◽  
Critical Role ◽  
Bacterial Pathogen ◽  
Human Macrophage ◽  
Antiapoptotic Activity

ABSTRACT Coxiella burnetii is an obligate intracellular bacterial pathogen that directs biogenesis of a lysosome-like, parasitophorous vacuole in mammalian cells. We recently reported that C. burnetii inhibits apoptotic cell death in macrophages, presumably as a mechanism to sustain the host for completion of its lengthy infectious cycle. In the current study, we further investigated C. burnetii manipulation of host cell signaling and apoptosis by examining the effect of C. burnetii infection on activation of 15 host proteins involved in stress responses, cytokine production, and apoptosis. C. burnetii infection of THP-1 human macrophage-like cells caused increased levels of phosphorylated c-Jun, Hsp27, Jun N-terminal protein kinase, and p38 at 2 h postinfection (hpi), and this activation rapidly decreased to near basal levels by 24 hpi. The prosurvival kinases Akt and Erk1/2 (extracellular signal-regulated kinases 1 and 2) were also activated at 2 to 6 hpi; however, the phosphorylation of these proteins increased coincident with C. burnetii replication through at least 72 hpi. Sustained phosphorylation of Akt and Erk1/2 was abolished by treatment of infected cells with rifampin, indicating their activation is a C. burnetii-directed event requiring pathogen RNA synthesis. Moreover, pharmacological inhibition of Akt or Erk1/2 significantly decreased C. burnetii antiapoptotic activity. Collectively, these results indicate the importance of C. burnetii modulation of host signaling and demonstrate a critical role for Akt and Erk1/2 in successful intracellular parasitism and maintenance of host cell viability.

scholarly journals Mammalian Cell Culture Clarification: A Case Study Using Chimeric Anti-CEA Monoclonal Antibodies

2011 ◽  
Vol 12 (4) ◽  
Author(s):  
Mohamed Ali Abol Hassan ◽  
Abdul Wahab Mohammad ◽  
And Badarulhisam Abdul Rahman
Keyword(s):  
Cell Culture ◽  
Monoclonal Antibodies ◽  
Host Cell ◽  
Cell Lines ◽  
Mammalian Cell ◽  
Mammalian Cells ◽  
Culture Media ◽  
Mammalian Cell Culture ◽  
Host Cell Proteins ◽  
Depth Filtration

The extracellular expression of monoclonal antibodies (mAbs) in mammalian cell culture provides both opportunities and restrictions for the design of robust harvest and clarification operations. With advances in cell culture media and cell lines, it is now possible to achieve high titers of over 5 g/l for mAbs. However, Mammalian cells are sensitive to breakage due to shear stress that can result in release of proteases and other host cell proteins (HCPs) which eventually affects product stability and purity. There is larger number of mAbs undergoing clinical development and it has placed significant importance on platform technologies of process development. Generally, Centrifugation and microfiltration are the primary harvest techniques used in the industry and depth filtration is also used as a step operation on clarification. This study compares the unit operations; centrifugation, microfiltration and depth filtration for maximum recovery of monoclonal antibodies. The results have shown that the depth filtration as more suitable operation for mammalian cell culture clarification since it gives 96% recovery of mAbs in comparison to centrifugation and microfiltration. ABSTRAK: Pengungkapan luar sel dari antibodi monoklon (monoclonal antibodies ((mAbs) dalam kultur sel mamalia memberi ruang dan batasan terhadap reka bentuk penuaian yang cekap dan penerangan operasi. Dengan kemajuan dalam media sel kultur dan cell lines (produk yang berupa sel kekal yang digunakan untuk tujuan kajian biologi), kini adalah berkemungkinan untuk memperolehi titer tinggi melebihi 5g/l untuk mAbs [2]. Walaupun begitu, sel mamalia sensitif terhadap retakan disebabkan tegasan ricih yang menyebabkan pengeluaran protease dan hos sel protein yang lain, (host cell proteins (HCPs)) akhirnya mempengaruhi kestabilan dan keaslian produk. Terdapat mAbs dalam jumlah besar yang masih menjalani pembangunan klinikal dan sesungguhnya ini penting sebagai satu landasan teknologi dalam proses pembangunan. Umumnya pengemparan dan mikropenurasan merupakan teknik asas tuaian dalam industri dan penurasan dalam juga digunakan sebagai satu pengendalian langkah dalam penjelasannya. Kajian ini membandingkan operasi unit: pengemparan, mikropenurasan dan penurasan dalam untuk perolehan antibodi monoklon yang maksima. Keputusan menunjukkan penurasan dalam adalah operasi yang lebih sesuai untuk penjelasan kultur sel mamalia kerana ia memberikan perolehan 96 % mAbs berbandingkan dengan cara pengemparan dan mikropenurasan.

scholarly journals Listeria monocytogenes Exploits Normal Host Cell Processes to Spread from Cell to Cell✪

1999 ◽  
Vol 146 (6) ◽  
pp. 1333-1350 ◽  
Author(s):  
Jennifer R. Robbins ◽  
Angela I. Barth ◽  
Hélène Marquis ◽  
Eugenio L. de Hostos ◽  
W. James Nelson ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Host Cell ◽  
Mdck Cells ◽  
Recipient Cell ◽  
Cell Monolayer ◽  
Bacterial Pathogen ◽  
Host Cells ◽  
Turnover Rates ◽  
Membrane Bound ◽  
Intercellular Spread

The bacterial pathogen, Listeria monocytogenes, grows in the cytoplasm of host cells and spreads intercellularly using a form of actin-based motility mediated by the bacterial protein ActA. Tightly adherent monolayers of MDCK cells that constitutively express GFP-actin were infected with L. monocytogenes, and intercellular spread of bacteria was observed by video microscopy. The probability of formation of membrane-bound protrusions containing bacteria decreased with host cell monolayer age and the establishment of extensive cell-cell contacts. After their extension into a recipient cell, intercellular membrane-bound protrusions underwent a period of bacterium-dependent fitful movement, followed by their collapse into a vacuole and rapid vacuolar lysis. Actin filaments in protrusions exhibited decreased turnover rates compared with bacterially associated cytoplasmic actin comet tails. Recovery of motility in the recipient cell required 1–2 bacterial generations. This delay may be explained by acid-dependent cleavage of ActA by the bacterial metalloprotease, Mpl. Importantly, we have observed that low levels of endocytosis of neighboring MDCK cell surface fragments occurs in the absence of bacteria, implying that intercellular spread of bacteria may exploit an endogenous process of paracytophagy.

scholarly journals Association of Rap1a and Rap1b proteins with late endocytic/phagocytic compartments and Rap2a with the Golgi complex

1994 ◽  
Vol 107 (6) ◽  
pp. 1661-1670 ◽  
Author(s):  
V. Pizon ◽  
M. Desjardins ◽  
C. Bucci ◽  
R.G. Parton ◽  
M. Zerial
Keyword(s):  
Golgi Complex ◽  
Mammalian Cells ◽  
Subcellular Fractionation ◽  
Small Gtpases ◽  
Intracellular Location ◽  
Confocal Immunofluorescence Microscopy ◽  
Late Endosomes ◽  
Confocal Immunofluorescence ◽  
Ras Family ◽  
Endocytic Compartments

Among the small GTPases of the Ras family, Rap proteins exhibit the highest homology with p21Ras. The four Rap proteins so far identified constitute two subgroups, comprising the Rap1(A,B) and the Rap2(A,B) proteins. The intracellular location of Rap1A, Rap1B and Rap2A proteins was investigated in mammalian cells by confocal immunofluorescence microscopy. Using a specific anti-Rap1 affinity-purified antibody, both Rap1A and Rap1B proteins were localized to late endocytic compartments (late endosomes/lysosomes) in fibroblasts. The localization of the Rap1A and B proteins transiently overexpressed with the vaccinia T7 system was identical to that observed for endogenous Rap1 proteins. In contrast, epitope-tagged Rap2A protein colocalized with several markers of the Golgi complex, thus indicating that its site of function was distinct from that of Rap1A. In addition, morphological and subcellular fractionation studies provided evidence for the association of Rap1 proteins with phagosomes displaying biochemical features of late endocytic structures in J774 macrophages. Thus, the localization of Rap1A and Rap1B implicates their involvement in late endocytic/phagocytic processes.

scholarly journals Evolution and Adaptation of Legionella pneumophila to Manipulate the Ubiquitination Machinery of Its Amoebae and Mammalian Hosts

Biomolecules ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 112
Author(s):  
Christopher T.D. Price ◽  
Yousef Abu Kwaik
Keyword(s):  
Host Cell ◽  
Legionella Pneumophila ◽  
Mammalian Cells ◽  
Bacterial Pathogen ◽  
Structural Similarity ◽  
Ubiquitin Pathway ◽  
Diverse Range ◽  
E3 Ligases ◽  
Environmental Bacterium ◽  
Natural Hosts

The ubiquitin pathway is highly conserved across the eukaryotic domain of life and plays an essential role in a plethora of cellular processes. It is not surprising that many intracellular bacterial pathogens often target the essential host ubiquitin pathway. The intracellular bacterial pathogen Legionella pneumophila injects into the host cell cytosol multiple classes of classical and novel ubiquitin-modifying enzymes that modulate diverse ubiquitin-related processes in the host cell. Most of these pathogen-injected proteins, designated as effectors, mimic known E3-ubiquitin ligases through harboring F-box or U-box domains. The classical F-box effector, AnkB targets host proteins for K48-linked polyubiquitination, which leads to excessive proteasomal degradation that is required to generate adequate supplies of amino acids for metabolism of the pathogen. In contrast, the SidC and SdcA effectors share no structural similarity to known eukaryotic ligases despite having E3-ubiquitin ligase activity, suggesting that the number of E3-ligases in eukaryotes is under-represented. L. pneumophila also injects into the host many novel ubiquitin-modifying enzymes, which are the SidE family of effectors that catalyze phosphoribosyl-ubiquitination of serine residue of target proteins, independently of the canonical E1-2-3 enzymatic cascade. Interestingly, the environmental bacterium, L. pneumophila, has evolved within a diverse range of amoebal species, which serve as the natural hosts, while accidental transmission through contaminated aerosols can cause pneumonia in humans. Therefore, it is likely that the novel ubiquitin-modifying enzymes of L. pneumophila were acquired by the pathogen through interkingdom gene transfer from the diverse natural amoebal hosts. Furthermore, conservation of the ubiquitin pathway across eukaryotes has enabled these novel ubiquitin-modifying enzymes to function similarly in mammalian cells. Studies on the biological functions of these effectors are likely to reveal further novel ubiquitin biology and shed further lights on the evolution of ubiquitin.

scholarly journals Dynamic proteomics profiling of Legionella pneumophila infection unveils modulation of the host mitochondrial stress response pathway

2020 ◽  
Author(s):  
Julia Noack ◽  
David Jimenez-Morales ◽  
Erica Stevenson ◽  
Tom Moss ◽  
Gwendolyn Jang ◽  
...  
Keyword(s):  
Stress Response ◽  
Host Cell ◽  
Legionella Pneumophila ◽  
Mammalian Cells ◽  
Bacterial Pathogen ◽  
Effector Proteins ◽  
Mitochondrial Stress ◽  
Cellular Targets ◽  
Mitochondrial Proteome ◽  
Cell Proteome

SUMMARYThe human pathogen Legionella pneumophila (L.p.) secretes ~330 bacterial effector proteins into the host cell which interfere with numerous cellular pathways and often regulate host cell proteins through post-translational modifications. However, the cellular targets and functions of most L.p. effectors are not known. In order to obtain a global overview of potential targets of these effectors, we analyzed the host cell proteome, ubiquitinome, and phosphoproteome during L.p. infection. Our analysis reveals dramatic spatiotemporal changes in the host cell proteome that are dependent on the secretion of bacterial effectors. Strikingly, we show that L.p. substantially reshapes the mitochondrial proteome and modulates mitochondrial stress response pathways such as the mitochondrial unfolded protein response (UPRmt). To our knowledge, this is the first evidence of manipulation of the UPRmt by a bacterial pathogen in mammalian cells. In addition, we have identified a previously uncharacterized L.p. effector that is targeted to host cell mitochondria and protects mitochondrial network integrity during mitochondrial stress.

The rab7 GTPase resides on a vesicular compartment connected to lysosomes

1995 ◽  
Vol 108 (11) ◽  
pp. 3349-3358 ◽  
Author(s):  
S. Meresse ◽  
J.P. Gorvel ◽  
P. Chavrier
Keyword(s):  
Mammalian Cells ◽  
Intracellular Localization ◽  
Confocal Laser ◽  
Cell Periphery ◽  
Rab Gtpases ◽  
Wild Type ◽  
Microtubule Network ◽  
Late Endosomes ◽  
Hela Cell Lines ◽  
Vesicular Compartment

Rab GTPases belong to the Ras GTPase superfamily and are key regulators of membrane traffic. Among them, rab7 has been localized on late endosomes of NRK cells but its function remains unknown. In order to investigate its role, we generated stable HeLa cell lines that express either wild type or a GTPase-defective mutant of rab7 in an inducible manner. A morphological analysis of the intracellular localization of these proteins was performed by confocal laser microscopy. Here we show that, in HeLa cells, rab7 is present on a vesicular compartment that extends from the perinuclear area to the cell periphery and shows only a partial colocalization with the cation-independent mannose 6-phosphate receptor, a marker for late endosomes. The topology of this compartment is dependent on the microtubule network since nocodazole treatment results in its scattering throughout the cytoplasm. In addition, we observed that, in contrast to the wild-type protein, a rab7 mutant with a reduced GTPase activity is in part associated with lysosomal membranes. This observation was confirmed by subcellular fractionation in a Percoll gradient. Our data implicate rab7 as the first GTPase functioning on terminal endocytic structures in mammalian cells.

scholarly journals Host cell invasion by trypanosomes requires lysosomes and microtubule/kinesin-mediated transport.

1996 ◽  
Vol 134 (2) ◽  
pp. 349-362 ◽  
Author(s):  
A Rodríguez ◽  
E Samoff ◽  
M G Rioult ◽  
A Chung ◽  
N W Andrews
Keyword(s):  
Host Cell ◽  
Mammalian Cells ◽  
Parasitophorous Vacuole ◽  
Attachment Site ◽  
Protozoan Parasite ◽  
Time Lapse ◽  
Host Cells ◽  
Original Position ◽  
Cell Periphery ◽  
Entry Site

Invasion of mammalian cells by the protozoan parasite Trypanosoma cruzi occurs by an actin-independent mechanism distinct from phagocytosis. Clusters of host lysosomes are observed at the site of parasite attachment, and lysosomal markers are detected in the vacuolar membrane at early stages of the entry process. These observations led to the hypothesis that the trypanosomes recruit host lysosomes to their attachment site, and that lysosomal fusion serves as a source of membrane to form the parasitophorous vacuole. Here we directly demonstrate directional migration of lysosomes to the parasite entry site, using time-lapse video-enhanced microscopy of L6E9 myoblasts exposed to T. cruzi trypomastigotes. BSA-gold-loaded lysosomes moved towards the cell periphery, in the direction of the parasite attachment site, but only when their original position was less than 11-12 microns from the invasion site. Lysosomes more distant from the invasion area exhibited only the short multi-directional saltatory movements previously described for lysosomes, regardless of their proximity to the cell margins. Specific depletion of peripheral lysosomes was obtained by microinjection of NRK cells with antibodies against the cytoplasmic domain of lgp 120, a treatment that aggregated lysosomes in the perinuclear area and inhibited T. cruzi entry. The microtubule-binding drugs nocodazole, colchicine, vinblastine, and taxol also inhibited invasion, in both NRK and L6E9 cells. Furthermore, microinjection of antibodies to the heavy chain of kinesin blocked the acidification-induced, microtubule-dependent redistribution of lysosomes to the host cell periphery, and reduced trypomastigote entry. Our results therefore demonstrate that during T. cruzi invasion of host cells lysosomes are mobilized from the immediately surrounding area, and that availability of lysosomes at the cell periphery and microtubule/kinesin-mediated transport are requirements for parasite entry.

scholarly journals Precision analysis for the determination of steric mass action parameters using eight tobacco host cell proteins

2021 ◽  
pp. 462379
Author(s):  
C.R. Bernau ◽  
R.C. Jäpel ◽  
J.W. Hübbers ◽  
S. Nölting ◽  
P. Opdensteinen ◽  
...  
Keyword(s):  
Host Cell ◽  
Mass Action ◽  
Precision Analysis ◽  
Host Cell Proteins

scholarly journals Compounds that target host cell proteins prevent varicella-zoster virus replication in culture, ex vivo, and in SCID-Hu mice

2010 ◽  
Vol 86 (3) ◽  
pp. 276-285 ◽  
Author(s):  
Jenny Rowe ◽  
Rebecca J. Greenblatt ◽  
Dongmei Liu ◽  
Jennifer F. Moffat
Keyword(s):  
Varicella Zoster Virus ◽  
Host Cell ◽  
Virus Replication ◽  
Ex Vivo ◽  
Varicella Zoster ◽  
Host Cell Proteins
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