genetic-engineering-dictyostelium-discoideum-cells-based-on-selection

Genetic Engineering of <em>Dictyostelium discoideum</em> Cells Based on Selection and Growth on Bacteria

Dictyostelium discoideum is an intriguing model organism for the study of cell differentiation processes during development, cell signaling, and other ...

MRC Laboratory of Molecular Biology

Macropinocytosis is a conserved endocytic process used by  amoebae for feeding on liquid medium. To further  as a model for macropinocytosis, we developed a high-throughput flow cytometry assay to measure macropinocytosis, and used it to identify inhibitors and investigate the physiological regulation of macropinocytosis.  has two feeding states: phagocytic and macropinocytic. When cells are switched from phagocytic growth on bacteria to liquid media, the rate of macropinocytosis slowly increases, due to increased size and frequency of macropinosomes. Upregulation is triggered by a minimal medium containing three amino acids plus glucose and likely depends on macropinocytosis itself. The presence of bacteria suppresses macropinocytosis while their product, folate, partially suppresses upregulation of macropinocytosis. Starvation, which initiates development, does not of itself suppress macropinocytosis: this can continue in isolated cells, but is shut down by a conditioned-medium factor or activation of PKA signalling. Thus macropinocytosis is a facultative ability of  cells, regulated by environmental conditions that are identified here.This article has an associated First Person interview with the first author of the paper.

The physiological regulation of macropinocytosis during  growth and development.

Macropinocytosis is an actin-driven process of large-scale, non-specific fluid uptake used for feeding by some cancer cells and the macropinocytosis model organism  In , macropinocytic cups are organised by 'macropinocytic patches' in the plasma membrane. These contain activated Ras, Rac and PI(3,4,5)P3 and direct actin polymerisation to their periphery. We show that an Akt (PkbA) and an SGK (PkbR1) protein kinase act downstream of PI(3,4,5)P3 and are together nearly essential for fluid uptake. This pathway enables the formation of larger macropinocytic patches and macropinosomes, thereby dramatically increasing fluid uptake. Through phosphoproteomics, we identify a RhoGAP, GacG, as a PkbA/PkbR1 target and show it is required for efficient macropinocytosis and expansion of macropinocytic patches. The function of Akt and SGK in cell feeding through control of macropinosome size has implications for cancer cell biology.

Article	Year
The physiological regulation of macropinocytosis during growth and development. Journal of cell science\| PubMed ID: 29440238	2018
Akt and SGK protein kinases are required for efficient feeding by macropinocytosis. Journal of cell science\| PubMed ID: 30617109	2019

Thomas D. Williams

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