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Neurofibromin controls macropinocytosis and phagocytosis in Dictyostelium.

Bloomfield G, Traynor D, Sander SP, Veltman DM, Pachebat JA, Kay RR - Elife (2015)

Bottom Line: Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis.An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling.Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.

ABSTRACT
Cells use phagocytosis and macropinocytosis to internalise bulk material, which in phagotrophic organisms supplies the nutrients necessary for growth. Wildtype Dictyostelium amoebae feed on bacteria, but for decades laboratory work has relied on axenic mutants that can also grow on liquid media. We used forward genetics to identify the causative gene underlying this phenotype. This gene encodes the RasGAP Neurofibromin (NF1). Loss of NF1 enables axenic growth by increasing fluid uptake. Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis. Relatedly, NF1 mutants can ingest larger-than-normal particles using phagocytosis. An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling. Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures.

No MeSH data available.


Related in: MedlinePlus

NF1 mutants grow and develop when grown on bacterial lawns.DdB (WT) and HM1591 (axeB ) spores were plated clonally on SM agar plates in association with Klebsiella pneumoniae. After 5 days, plaques of amoebae growing outwards on the bacterial lawn were photographed; aggregates and fruiting bodies are visible where the bacteria have been cleared causing the amoebae to enter their asexual developmental cycle (scale = 5 mm). Fruiting bodies in the mutant tend to be smaller than wildtype, but otherwise do not show obvious defects.DOI:http://dx.doi.org/10.7554/eLife.04940.028
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fig7s1: NF1 mutants grow and develop when grown on bacterial lawns.DdB (WT) and HM1591 (axeB ) spores were plated clonally on SM agar plates in association with Klebsiella pneumoniae. After 5 days, plaques of amoebae growing outwards on the bacterial lawn were photographed; aggregates and fruiting bodies are visible where the bacteria have been cleared causing the amoebae to enter their asexual developmental cycle (scale = 5 mm). Fruiting bodies in the mutant tend to be smaller than wildtype, but otherwise do not show obvious defects.DOI:http://dx.doi.org/10.7554/eLife.04940.028


Neurofibromin controls macropinocytosis and phagocytosis in Dictyostelium.

Bloomfield G, Traynor D, Sander SP, Veltman DM, Pachebat JA, Kay RR - Elife (2015)

NF1 mutants grow and develop when grown on bacterial lawns.DdB (WT) and HM1591 (axeB ) spores were plated clonally on SM agar plates in association with Klebsiella pneumoniae. After 5 days, plaques of amoebae growing outwards on the bacterial lawn were photographed; aggregates and fruiting bodies are visible where the bacteria have been cleared causing the amoebae to enter their asexual developmental cycle (scale = 5 mm). Fruiting bodies in the mutant tend to be smaller than wildtype, but otherwise do not show obvious defects.DOI:http://dx.doi.org/10.7554/eLife.04940.028
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4374526&req=5

fig7s1: NF1 mutants grow and develop when grown on bacterial lawns.DdB (WT) and HM1591 (axeB ) spores were plated clonally on SM agar plates in association with Klebsiella pneumoniae. After 5 days, plaques of amoebae growing outwards on the bacterial lawn were photographed; aggregates and fruiting bodies are visible where the bacteria have been cleared causing the amoebae to enter their asexual developmental cycle (scale = 5 mm). Fruiting bodies in the mutant tend to be smaller than wildtype, but otherwise do not show obvious defects.DOI:http://dx.doi.org/10.7554/eLife.04940.028
Bottom Line: Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis.An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling.Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.

ABSTRACT
Cells use phagocytosis and macropinocytosis to internalise bulk material, which in phagotrophic organisms supplies the nutrients necessary for growth. Wildtype Dictyostelium amoebae feed on bacteria, but for decades laboratory work has relied on axenic mutants that can also grow on liquid media. We used forward genetics to identify the causative gene underlying this phenotype. This gene encodes the RasGAP Neurofibromin (NF1). Loss of NF1 enables axenic growth by increasing fluid uptake. Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis. Relatedly, NF1 mutants can ingest larger-than-normal particles using phagocytosis. An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling. Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures.

No MeSH data available.


Related in: MedlinePlus