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Lysosomotropic agents activate the capacity for calcium dependent pinocytosis in starved Amoeba proteus: Evidence for a mechanism involving phospholipase A2.

Vult von Steyern, Fredrik LU ; Falck, B and Josefsson, Jan-Owe LU (1996) In Protoplasma 192(1-2). p.20-27
Abstract
Pinocytosis induced by Na+ was assayed by phase contrast microscopy in 8–12 days starvedAmoeba proteus. These cultures were inactive with respect to calcium-dependent Na+-induced pinocytosis, but treatment with amino acid methyl and ethyl esters increased their capacity for pinocytosis. Besides promoting pinocytosis these compounds also stimulated calcium-sensitive secretion of lysosomal enzymes from normal, 2–3 days starved, cells. Only uncharged 1-forms of the amino acid esters were effective. Also other lysosomotropic compounds including monodansylcadaverine, glycine-phenylalanine-2-naphthylamide, NH4Cl, and the ionophores monensin and A23187 activated starved cells. The effect of these agents (except A23187) was inhibited by the drug... (More)
Pinocytosis induced by Na+ was assayed by phase contrast microscopy in 8–12 days starvedAmoeba proteus. These cultures were inactive with respect to calcium-dependent Na+-induced pinocytosis, but treatment with amino acid methyl and ethyl esters increased their capacity for pinocytosis. Besides promoting pinocytosis these compounds also stimulated calcium-sensitive secretion of lysosomal enzymes from normal, 2–3 days starved, cells. Only uncharged 1-forms of the amino acid esters were effective. Also other lysosomotropic compounds including monodansylcadaverine, glycine-phenylalanine-2-naphthylamide, NH4Cl, and the ionophores monensin and A23187 activated starved cells. The effect of these agents (except A23187) was inhibited by the drug dantrolene suggesting that activation is a consequence of release of Ca2+ from intracellular stores. Several of the lysosomotropic agents also lost their activating effect in the presence of phospholipase A2 (PLA2) inhibitors. To investigate whether or not PLA2 activity in the cell culture could imitate the effect of the lysosomotropic agents, we incubated starved cells with snake venom PLA2s. These enzymes caused rapid, dantrolene-sensitive activation of the cells. Measurement of endogenous PLA2in ldquonormalrdquo cells revealed significant cellular activity but no significant secretion of the enzyme into the culture medium was observed. Together the studies with enzyme inhibitors and dantrolene suggest that the process by which lysosomotropic agents affect pinocytosis involves activation of PLA2 and release of Ca2+ from intracellular stores. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Phospholipase A2, Calcium, Amino acid ester, Endocytosis, Dantrolene, Lysosome
in
Protoplasma
volume
192
issue
1-2
pages
20 - 27
publisher
Springer
external identifiers
  • scopus:0013658301
ISSN
1615-6102
DOI
10.1007/BF01273241
language
English
LU publication?
yes
id
42dfc792-6a0e-4de6-bdd7-288d71618308 (old id 1110837)
date added to LUP
2008-07-30 09:36:41
date last changed
2017-01-01 04:52:33
@article{42dfc792-6a0e-4de6-bdd7-288d71618308,
  abstract     = {Pinocytosis induced by Na+ was assayed by phase contrast microscopy in 8–12 days starvedAmoeba proteus. These cultures were inactive with respect to calcium-dependent Na+-induced pinocytosis, but treatment with amino acid methyl and ethyl esters increased their capacity for pinocytosis. Besides promoting pinocytosis these compounds also stimulated calcium-sensitive secretion of lysosomal enzymes from normal, 2–3 days starved, cells. Only uncharged 1-forms of the amino acid esters were effective. Also other lysosomotropic compounds including monodansylcadaverine, glycine-phenylalanine-2-naphthylamide, NH4Cl, and the ionophores monensin and A23187 activated starved cells. The effect of these agents (except A23187) was inhibited by the drug dantrolene suggesting that activation is a consequence of release of Ca2+ from intracellular stores. Several of the lysosomotropic agents also lost their activating effect in the presence of phospholipase A2 (PLA2) inhibitors. To investigate whether or not PLA2 activity in the cell culture could imitate the effect of the lysosomotropic agents, we incubated starved cells with snake venom PLA2s. These enzymes caused rapid, dantrolene-sensitive activation of the cells. Measurement of endogenous PLA2in ldquonormalrdquo cells revealed significant cellular activity but no significant secretion of the enzyme into the culture medium was observed. Together the studies with enzyme inhibitors and dantrolene suggest that the process by which lysosomotropic agents affect pinocytosis involves activation of PLA2 and release of Ca2+ from intracellular stores.},
  author       = {Vult von Steyern, Fredrik and Falck, B and Josefsson, Jan-Owe},
  issn         = {1615-6102},
  keyword      = {Phospholipase A2,Calcium,Amino acid ester,Endocytosis,Dantrolene,Lysosome},
  language     = {eng},
  number       = {1-2},
  pages        = {20--27},
  publisher    = {Springer},
  series       = {Protoplasma},
  title        = {Lysosomotropic agents activate the capacity for calcium dependent pinocytosis in starved Amoeba proteus: Evidence for a mechanism involving phospholipase A2.},
  url          = {http://dx.doi.org/10.1007/BF01273241},
  volume       = {192},
  year         = {1996},
}