open access

Vol 49, No 2 (2011)
Original paper
Published online: 2011-07-11
Submitted: 2011-12-19
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Characteristics of weak base-induced vacuoles formed around individual acidic organelles

Hiromi Hiruma, Tadashi Kawakami
DOI: 10.5603/FHC.2011.0038
·
Folia Histochem Cytobiol 2011;49(2):272-279.

open access

Vol 49, No 2 (2011)
ORIGINAL PAPERS
Published online: 2011-07-11
Submitted: 2011-12-19

Abstract

We have previously found that the weak base 4-aminopyridine induces Brownian motion of acidic organelles around which vacuoles are formed, causing organelle traffic disorder in neurons. Our present study investigated the characteristics of vacuoles induced by weak bases (NH4Cl, aminopyridines, and chloroquine) using mouse cells. Individual vacuoles included acidic organelles identified by fluorescent protein expression. Mitochondria and actin filaments were extruded outside the vacuoles, composing the vacuole rim. Staining with amine-reactive fluorescence showed no protein/amino acid content in vacuoles. Thus, serous vacuolar contents are probably partitioned by viscous cytosol, other organelles, and cytoskeletons, but not membrane. The weak base (chloroquine) was immunochemically detected in intravacuolar organelles, but not in vacuoles. Early vacuolization was reversible, but long-term vacuolization caused cell death. The vacuolization and cell death were blocked by the vacuolar H+-ATPase inhibitor and Cl–-free medium. Staining with LysoTracker or LysoSensor indicated that intravacuolar organelles were strongly acidic and vacuoles were slightly acidic. This suggests that vacuolization is caused by accumulation of weak base and H+ in acidic organelles, driven by vacuolar H+-ATPase associated with Cl entering, and probably by subsequent extrusion of H+ and water from organelles to the surrounding cytoplasm. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 2, pp. 272–279)

Abstract

We have previously found that the weak base 4-aminopyridine induces Brownian motion of acidic organelles around which vacuoles are formed, causing organelle traffic disorder in neurons. Our present study investigated the characteristics of vacuoles induced by weak bases (NH4Cl, aminopyridines, and chloroquine) using mouse cells. Individual vacuoles included acidic organelles identified by fluorescent protein expression. Mitochondria and actin filaments were extruded outside the vacuoles, composing the vacuole rim. Staining with amine-reactive fluorescence showed no protein/amino acid content in vacuoles. Thus, serous vacuolar contents are probably partitioned by viscous cytosol, other organelles, and cytoskeletons, but not membrane. The weak base (chloroquine) was immunochemically detected in intravacuolar organelles, but not in vacuoles. Early vacuolization was reversible, but long-term vacuolization caused cell death. The vacuolization and cell death were blocked by the vacuolar H+-ATPase inhibitor and Cl–-free medium. Staining with LysoTracker or LysoSensor indicated that intravacuolar organelles were strongly acidic and vacuoles were slightly acidic. This suggests that vacuolization is caused by accumulation of weak base and H+ in acidic organelles, driven by vacuolar H+-ATPase associated with Cl entering, and probably by subsequent extrusion of H+ and water from organelles to the surrounding cytoplasm. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 2, pp. 272–279)
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Keywords

acidic organelles; cytoplasmic vacuoles; vacuolar H+-ATPase; weak base

About this article
Title

Characteristics of weak base-induced vacuoles formed around individual acidic organelles

Journal

Folia Histochemica et Cytobiologica

Issue

Vol 49, No 2 (2011)

Article type

Original paper

Pages

272-279

Published online

2011-07-11

DOI

10.5603/FHC.2011.0038

Bibliographic record

Folia Histochem Cytobiol 2011;49(2):272-279.

Keywords

acidic organelles
cytoplasmic vacuoles
vacuolar H+-ATPase
weak base

Authors

Hiromi Hiruma
Tadashi Kawakami

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