Affiliation:
1. MRC-Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
Abstract
Macropinocytosis—the large-scale, non-specific uptake of fluid by cells—is used by
Dictyostelium discoideum
amoebae to obtain nutrients. These cells form circular ruffles around regions of membrane defined by a patch of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) and the activated forms of the small G-proteins Ras and Rac. When this ruffle closes, a vesicle of the medium is delivered to the cell interior for further processing. It is accepted that PIP3 is required for efficient macropinocytosis. Here, we assess the roles of Ras and Rac in
Dictyostelium
macropinocytosis. Gain-of-function experiments show that macropinocytosis is stimulated by persistent Ras activation and genetic analysis suggests that RasG and RasS are the key Ras proteins involved. Among the activating guanine exchange factors (GEFs), GefF is implicated in macropinocytosis by an insertional mutant. The individual roles of Rho family proteins are little understood but activation of at least some may be independent of PIP3.
This article is part of the Theo Murphy meeting issue ‘Macropinocytosis’.
Subject
General Agricultural and Biological Sciences,General Biochemistry, Genetics and Molecular Biology
Cited by
24 articles.
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