Origin, originality, functions, subversions and molecular signalling of macropinocytosis

doi:10.1078/1438-4221-00157

International Journal of Medical Microbiology

Volume 291, Issues 6–7, 2001, Pages 487-494

https://doi.org/10.1078/1438-4221-00157 Get rights and content

Abstract

Macropinocytosis refers to the formation of primary large endocytic vesicles of irregular size and shape, generated by actin-driven evaginations of the plasma membrane, whereby cells avidly incorporate extracellular fluid. Macropinosomes resemble “empty” phagosomes and show no difference with the “spacious phagosomes” triggered by the enteropathogenic bacteria Salmonella and Shigella. Macropinosomes may fuse with lysosomes or regurgitate their content back to the extracellular space. In multiple cell types, macropinocytosis is a transient response to growth factors. When amoebas are cultured under axenic conditions, macropinocytosis is induced so as to fulfil nutritional requirements. In immature dendritic cells, macropinocytosis allows for extensive sampling of soluble antigens; after a few days of maturation, this activity vanishes as processed peptides are being presented. Macropinosomes are also formed at the leading edge of motile leukocytes or neurons. In all these examples, macropinocytosis appears tightly regulated. Transformation of fibroblasts by Src or Ras also results in constitutive formation of macropinosomes at “ruffling” zones, that could be related to accelerated cell motility.

Like phagocytosis, macropinocytosis depends on signalling to the actin cytoskeleton. We have explored this signalling in transformed cells. v-Src and K-Ras activate PI3K and PLC, as demonstrated by in situ production of the corresponding lipid products. Pharmacological inhibitors of PI3K and PLC and stable transfection leading to a dominant-negative PI3-kinase construct in transformed fibroblasts abolish macropinocytosis, demonstrating that both enzyme activities are essential. Conversely, stable transfection leading to a dominant-positive PI3K in non-transformed fibroblasts is sufficient to induce macropinocytosis. Combination of experiments allows to conclude that PI3K and PLC act in sequential order. In non-polarized cells expressing a thermosensitive v-Src mutant, v-Src kinase activation accelerates fluid-phase endocytosis. In polarized MDCK cells, this stimulation occurs selectively at the apical domain and the response is selectively abrogated by pharmacological inhibitors of PI3K and PLC.

Thus, two paradigmatic oncogenes cause constitutive macropinocytosis. For v-Src, this response is polarized at the apical membrane. It is suggested that, in enterocytes that do not normally phagocytose, the PI3K-PLC signalling pathway leading to selective induction of macropinocytosis at the luminal surface has been subverted by enteropathogenic bacteria to penetrate via “spacious phagosomes”.

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Origin, originality, functions, subversions and molecular signalling of macropinocytosis

Abstract

Mechanisms of phagocytosis in macrophages

Annu. Rev. Immunol.

Salmonella stimulate macrophage macropinocytosis and persist within spacious phagosomes

J. Exp. Med.

Constitutive macropinocytosis in oncogene-transformed fibroblasts depends on sequential permanent activation of phosphoinositide 3-kinase and phospholipase C

Mol. Biol. Cell

The invasion protein InIB from Listeria monocytogenes activates PLC-γ1 downstream from PI 3-kinase

Cell. Microbiol.

Membrane traffic during cell locomotion

Curr. Opin. Cell Biol.

Evidence for a recycling role for Rab7 in regulating a late step in endocytosis and in retention of lysosomal enzymes in Dictyostelium discoideum

Mol. Biol. Cell

Phagocytosis and macropinocytosis in Dictyostelium: phosphoinositide-based processes, biochemically distinct: a review

Traffic

Internalization pathway of C3b receptors in human neutrophils and its transmodulation by chemoattractant receptors stimulation

Cell Regul.

The axenic mutations and endocytosis in Dictyostelium

Methods Cell Biol.

Clathrin polymerisation is not required for bulk-phase endocytosis in rat fetal fibroblasts

J. Cell Biol.

Endocytosis in the emergence of eucaryotic life

Invasion of epithelial cells by Shigella flexneri induces tyrosine phosphorylation of cortactin by a pp60c-src-mediated signalling pathway

EMBO J.

Translocation of Src kinase to the cell periphery is mediated by the actin cytoskeleton under the control of the Rho family of small G proteins

J. Cell Biol.

Exploitation of mammalian host cell functions by bacterial pathogens

Science

Phosphoinositide kinases

Annu. Rev. Biochem.

Developmental control of endocytosis in dendritic cells by Cdc42

Cell

Actin microfilaments play a critical role in endocytosis at the apical but not the basolateral surface of polarized epithelial cells

J. Cell Biol.

Rho GTPases and the actin cytoskeleton

Science

The coated pit and macropinocytic pathways serve distinct endosome populations

J. Cell Biol.

Endocytosis of desmosomal plaques depends on intact actin filaments and leads to a nondegradative compartment

Eur. J. Cell Biol.

Down-regulation of the filamentous actin cross-linking activity of cortactin by Src-mediated tyrosine phosphorylation

J. Biol. Chem.

A role for phosphoinositide 3- kinase in bacterial invasion

Science

Association of cortactin with dynamic actin in lamellipodia and on endosomal vesicles

J. Cell Sci.