PIKfyve/Fab1 is required for efficient V-ATPase and hydrolase delivery to phagosomes, phagosomal killing, and restriction of Legionella infection
Preprint posted on 17 July 2018 https://www.biorxiv.org/content/early/2018/07/17/343301
Article now published in PLOS Pathogens at http://dx.doi.org/10.1371/journal.ppat.1007551
Context and Background:
Intracellular pathogens, such as Legionella pneumophila, are among the major causes of disease and death. Pathogens hijack host cells trying to create an intracellular environment favourable for their replication. Host cells on other hand have to develop and refine defence mechanisms to beat the invaders to the punch and get rid of them before the infection spreads (Flannagan RS et al., 2009).
Phagocytosis plays a crucial role in the host-pathogen interaction as it represents the main mechanism of clearance and degradation of the not-self. For this reason, extensive research has been funnelled into this field to grasp the phases of phagosome maturation, in a journey that from the early step of ingestion ultimately leads to the digestion of the invader. Shortly after the internalisation of a particle, the phagosome is acidified and loaded with antimicrobial peptides and hydrolases, thereby creating a non-permissive environment for pathogen survival. The timing of the delivery of these components to the phagosome is strictly regulated and relies on the interaction with phosphoinositol lipids (PIPs) (Bohdanowicz M. et al., 2013). Therefore, understanding the mechanism of PIPs production and how this relates to phagosome maturation can be extremely beneficial and clinically relevant.
The preprint in brief:
The work of Buckley at al. underlines the importance of the lipid kinase PIKfyve in early-phagosome maturation and pathogen killing, using Dictyostelium as a model system. The results reported in this preprint highlight a role for PIKfyve in the delivery of the V-ATPase pump and hydrolytic enzymes to the phagosome, favouring the formation of an acidic environment hostile to bacteria. PIP production is therefore essential for shielding host cells from a wide array of microbes.
Laboratory strains of Dictyostelium can either feed by micropinocytosis or by internalising bacteria. The group exploit this characteristic to study host-pathogen interaction and address how PIKfyve kinase activity favours the host. By analysing the ability of a PIKfyve mutant strain to reduce the turbidity of a bacterial suspension and to grow on bacteria, they quickly realised that PIKfyve mutants effectively uptook bacteria but their growth rate was reduced, meaning that one or more steps in phagosome maturation was altered. The work goes on taking a closer look at the process and analysing the rate of phagosome acidification.
They found that, in the absence of PIKfyve, acidification was much slower and not as efficient as in the control. This acidification defect was due to a much slower recruitment of the proton pump V-ATPase to the phagosome, as assessed by imaging the dynamics of GFP-tagged versions of the VTPase subunits VatM and VatB (GFP-VatM and GFP-VatB, respectively). In addition, PIKfyve mutant cells showed a lack of proteolitic activity despite the levels of hydrolytic enzymes, such as Cathepsin D being unchanged (if not higher) compared to control, suggesting again an improper delivery to the phagosome.
Given that acidification and proteolitic activity contribute to bacteria killing, Buckley at al. tested how PIKfyve defective cells performed when plated on layers of a panel of different non-pathogenic bacteria. PIKfyve mutants were unable to efficiently grow on any of the bacteria tested and phagocytosed bacteria survived more than 3 times longer than in the control. All together, these data suggest that PIKfyve has a general role in killing and digesting a broad range of microbes.
Is PIKfyve activity required to protect host cells from infection? To address this final but yet crucial point, PIKfyve mutant cells were grown in the presence of the opportunistic human pathogen Legionella pneumophila. As expected, bacteria uptake was unperturbed, but again, the invaders survived much longer in PIKfyve mutant cells. Most importantly, the group proved that the pathogen grew much more rapidly and to a much greater extent in cells lacking PIKfyve activity than in control, meaning that in the absence of PIKfyve Legionella stands a much better chance of creating a permissive environment for its own replication.
Phagosome maturation requires the sequential fusion with several membrane compartments until the formation of the phagolysosome, responsible for the final degradation of the invader. Several pathogens therefore have developed the ability to alter the composition and levels of phosphoinositol lipids on the phagosome membrane to avoid its fusion with the lysosome, thereby escaping digestion. Understanding how PIP levels are controlled is therefore clinically relevant and important to get a better understanding of host-pathogen interaction.
Questions to the authors:
- Is the mechanism of how bacteria manipulate PIP levels known? Could they achieve this by inactivating PIKfyve kinase?
- SNAREs and Rabs are important for membrane fusion. Is their localisation to phagosomes altered in PIKfyve-null cells? Is there any specific SNARE/Rab affected?
- In Drosophila, highly vacuolated macrophages are dramatically impaired in their migration (Evans I. et al. 2013). Given that PIKfyve-null cells are highly vacuolated and the enzyme evolutionary conserved, can you predict whether, as a secondary effect, the inhibition of the kinase would impair the patrolling activity of immune cells?
- Flannagan RS, Cosio G, Grinstein S. Antimicrobial mechanisms of phagocytes and bacterial evasion strategies. Nat Rev Microbiol. 2009;7(5):355-66. Epub 2009/04/17.
- Bohdanowicz M, Grinstein S. Role of phospholipids in endocytosis, phagocytosis, and macropinocytosis. Physiological reviews. 2013; 93(1): 69-106.
- Evans IR, Ghai PA, Urbančič V, Tan KL, Wood W. SCAR/WAVE-mediated processing of engulfed apoptotic corpses is essential for effective macrophage migration in Drosophila. Cell Death Differ. 2013 May; 20 (5): 709-20.
Posted on: 13 September 2018 , updated on: 17 September 2018Read preprint
Also in the cell biology category:
mTORC1 is required for differentiation of germline stem cells in the Drosophila melanogaster testis
|Selected by||Diego Sainz de la Maza|
Expansion microscopy at one nanometer resolution
|Selected by||Nadja Hümpfer|
Actin-driven protrusions generate rapid long-range membrane tension propagation in cells
|Selected by||Nicolaes Hyun-Kee Min|
preListscell biology category:in the
The advances in fibroblast biology preList explores the recent discoveries and preprints of the fibroblast world. Get ready to immerse yourself with this list created for fibroblasts aficionados and lovers, and beyond. Here, my goal is to include preprints of fibroblast biology, heterogeneity, fate, extracellular matrix, behavior, topography, single-cell atlases, spatial transcriptomics, and their matrix!
|List by||Osvaldo Contreras|
EMBL Synthetic Morphogenesis: From Gene Circuits to Tissue Architecture (2021)
A list of preprints mentioned at the #EESmorphoG virtual meeting in 2021.
|List by||Alex Eve|
A collection of preprints presented during the virtual meeting of the Federation of European Neuroscience Societies (FENS) in 2020
|List by||Ana Dorrego-Rivas|
Planar Cell Polarity – PCP
This preList contains preprints about the latest findings on Planar Cell Polarity (PCP) in various model organisms at the molecular, cellular and tissue levels.
|List by||Ana Dorrego-Rivas|
BioMalPar XVI: Biology and Pathology of the Malaria Parasite
[under construction] Preprints presented at the (fully virtual) EMBL BioMalPar XVI, 17-18 May 2020 #emblmalaria
|List by||Dey Lab, Samantha Seah|
Recent research from the field of cell polarity is summarized in this list of preprints. It comprises of studies focusing on various forms of cell polarity ranging from epithelial polarity, planar cell polarity to front-to-rear polarity.
|List by||Yamini Ravichandran|
Preprints recently presented at the virtual Allied Genetics Conference, April 22-26, 2020. #TAGC20
|List by||Maiko Kitaoka et al.|
A curated list of preprints related to Gastruloids (in vitro models of early development obtained by 3D aggregation of embryonic cells). Updated until July 2021.
|List by||Paul Gerald L. Sanchez and Stefano Vianello|
ECFG15 – Fungal biology
Preprints presented at 15th European Conference on Fungal Genetics 17-20 February 2020 Rome
|List by||Hiral Shah|
ASCB EMBO Annual Meeting 2019
A collection of preprints presented at the 2019 ASCB EMBO Meeting in Washington, DC (December 7-11)
|List by||Madhuja Samaddar et al.|
EMBL Seeing is Believing – Imaging the Molecular Processes of Life
Preprints discussed at the 2019 edition of Seeing is Believing, at EMBL Heidelberg from the 9th-12th October 2019
|List by||Dey Lab|
Preprints on autophagy and lysosomal degradation and its role in neurodegeneration and disease. Includes molecular mechanisms, upstream signalling and regulation as well as studies on pharmaceutical interventions to upregulate the process.
|List by||Sandra Malmgren Hill|
Lung Disease and Regeneration
This preprint list compiles highlights from the field of lung biology.
|List by||Rob Hynds|
A curated list of preprints related to cellular metabolism at Biorxiv by Pablo Ranea Robles from the Prelights community. Special interest on lipid metabolism, peroxisomes and mitochondria.
|List by||Pablo Ranea Robles|
BSCB/BSDB Annual Meeting 2019
Preprints presented at the BSCB/BSDB Annual Meeting 2019
|List by||Dey Lab|
This list of preprints is focused on work expanding our knowledge on mitochondria in any organism, tissue or cell type, from the normal biology to the pathology.
|List by||Sandra Franco Iborra|
Biophysical Society Annual Meeting 2019
Few of the preprints that were discussed in the recent BPS annual meeting at Baltimore, USA
|List by||Joseph Jose Thottacherry|
ASCB/EMBO Annual Meeting 2018
This list relates to preprints that were discussed at the recent ASCB conference.
|List by||Dey Lab, Amanda Haage|