The fully linked HTML version of this article has now been published.
JCS ePress
online publication date 31 Oct 2006
doi: 10.1242/jcs.03238
Research Article
Macropinocytosis: regulated coordination of endocytic and exocytic membrane traffic events
Sestina Falcone,
Emanuele Cocucci,
Paola Podini,
Tomas Kirchhausen,
Emilio Clementi,
and
Jacopo Meldolesi*
* Author for correspondence (e-mail: meldolesi.jacopo{at}hsr.it)
Macropinocytosis, a form of bulk uptake of fluid and solid cargo into cytoplasmic vacuoles, called macropinosomes, has been studied mostly in relation to antigen presentation. Early membrane traffic events occurring in this process are, however, largely unknown. Using human dendritic cells we show that a marked increase in the rate of macropinocytosis occurs a few minutes after application of two markers (small latex beads or dextran), depends on a slow intracellular Ca2+ concentration ([Ca2+]i) rise that precedes the PI3K-dependent step, and is preceded and accompanied by exocytosis of enlargeosomes compensating in part for the macropinocytic plasma membrane internalization. Unexpectedly, macropinosomes themselves, which share markers with endosomes, undergo Ca2+-dependent exocytosis so that, after 
20 minutes of continuous bead or dextran uptake, an equilibrium is reached preventing cells from overloading themselves with the organelles. Large [Ca2+]i increases induced by ionomycin trigger rapid (<1 minute) exocytic regurgitation of all macropinosomes, whereas endosomes remain apparently unaffected. We conclude that, in dendritic cells, the rate of macropinocytosis is not constant but increases in a regulated fashion, as previously shown in other cell types. Moreover, macropinosomes are not simple containers that funnel cargo to an endocytic pathway, but unique organelles, distinct from endosomes by their competence for regulated exocytosis and other membrane properties.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
|
|
 
C. G. Hansen and B. J. Nichols
Molecular mechanisms of clathrin-independent endocytosis
J. Cell Sci.,
June 1, 2009;
122(11):
1713 - 1721.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Mandrekar, Q. Jiang, C. Y. D. Lee, J. Koenigsknecht-Talboo, D. M. Holtzman, and G. E. Landreth
Microglia Mediate the Clearance of Soluble A{beta} through Fluid Phase Macropinocytosis
J. Neurosci.,
April 1, 2009;
29(13):
4252 - 4262.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
I. Malyukova, K. F. Murray, C. Zhu, E. Boedeker, A. Kane, K. Patterson, J. R. Peterson, M. Donowitz, and O. Kovbasnjuk
Macropinocytosis in Shiga toxin 1 uptake by human intestinal epithelial cells and transcellular transcytosis
Am J Physiol Gastrointest Liver Physiol,
January 1, 2009;
296(1):
G78 - G92.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. Bonanomi, E. F. Fornasiero, G. Valdez, S. Halegoua, F. Benfenati, A. Menegon, and F. Valtorta
Identification of a developmentally regulated pathway of membrane retrieval in neuronal growth cones
J. Cell Sci.,
November 15, 2008;
121(22):
3757 - 3769.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Cocucci, G. Racchetti, M. Rupnik, and J. Meldolesi
The regulated exocytosis of enlargeosomes is mediated by a SNARE machinery that includes VAMP4
J. Cell Sci.,
September 15, 2008;
121(18):
2983 - 2991.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. N. Birts, C. H. Barton, and D. C. Wilton
A Catalytically Independent Physiological Function for Human Acute Phase Protein Group IIA Phospholipase A2: CELLULAR UPTAKE FACILITATES CELL DEBRIS REMOVAL
J. Biol. Chem.,
February 22, 2008;
283(8):
5034 - 5045.
[Abstract]
[Full Text]
[PDF]
|
|
|
© The Company of Biologists Ltd 2006
