Irreversible and reversible pore formation by polymeric alkylpyridinium salts (poly-APS) from the sponge Reniera sarai.
1. In this study, we investigated the electrophysiological actions of a high molecular weight fraction, predominantly containing two polymeric 1,3-alkylpyridinium salts (poly-APS) of 5.5 and approximately 19 kDa isolated from the marine sponge Reniera sarai. The biological properties of poly-APS are of particular interest because this preparation may be used to deliver macromolecules into the intracellular environment without producing long-term damage to cells. Poly-APS (50-0.05 micro g ml(-1)) was applied to cultured dorsal root ganglion neurones or HEK 293 cells and changes in cell membrane properties were measured using whole-cell patch-clamp recording and fura-2 Ca(2+) imaging. 2. Poly-APS (50 micro g ml(-1)) evoked irreversible depolarisations in membrane potential and reductions in input resistance. However, doses of 5 micro g ml(-1) and less produced reversible effects on these cell membrane characteristics and on Ca(2+) permeability. 3. At 0.05 micro g ml(-1), poly-APS could robust transient increases in Ca(2+) permeability without damaging the neurones or subsequently attenuating Ca(2+) entry through voltage-activated channels. 4. Bathing cells in NaCl-based extracellular medium containing 1.5 mM zinc attenuated the irreversible and reversible effects of poly-APS on membrane properties (membrane potential, input resistance and whole-cell currents). In both DRG neurones and HEK 293 cells, zinc attenuated Ca(2+) entry evoked by poly-APS. These effects of zinc were only observed if zinc was continually present during poly-APS application. However, zinc failed to attenuate the actions of poly-APS if it was applied after the sponge toxin preparation had evoked changes in membrane properties. 5. In conclusion, the pore-forming preparation poly-APS can have dose-dependent interactions with cell membranes and at low doses these can be reversible. Additionally, the interactions between poly-APS and cell membranes could be attenuated by zinc.
McClelland
D
D
Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD.
Evans
R M
RM
Abidin
I
I
Sharma
S
S
Choudhry
F Z
FZ
Jaspars
M
M
Sepcić
K
K
Scott
R H
RH
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005727:Ganglia, Spinal / Q000166:cytology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000196:embryology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011108:Polymers / Q000302:isolation & purification / Q000494:pharmacology*; D011161:Porifera / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D015032:Zinc / Q000494:pharmacology
D011108:Polymers; D011726:Pyridinium Compounds; C115254:poly-APS; D015032:Zinc; D002118:Calcium