Acid-sensing ion channels in malignant gliomas.
High grade glioma cells derived from patient biopsies express an amiloride-sensitive sodium conductance that has properties attributed to the human brain sodium channel family, also known as acid-sensing ion channels (ASICs). This amiloride-sensitive conductance was not detected in cells obtained from normal brain tissue or low grade or benign tumors. Differential gene profiling data showed that ASIC1 and ASIC2 mRNA were present in normal and low grade tumor cells. Although ASIC1 was present in all of the high grade glial cells examined, ASIC2 mRNA was detected in less than half. The main purpose of our work was to examine the molecular mechanisms that may underlie the constitutively activated sodium currents present in high grade glioma cells. Our results show that 1) gain-of-function mutations of ASIC1 were not present in a number of freshly resected and cultured high grade gliomas, 2) syntaxin 1A inhibited ASIC currents only when ASIC1 and ASIC2 were co-expressed, and 3) the inhibition of ASIC currents by syntaxin 1A had an absolute requirement for either gamma- or delta-hENaC. Transfection of cultured cells originally derived from high grade gliomas (U87-MG and SK-MG1) with ASIC2 abolished basal amiloride-sensitive sodium conductance; this inhibition was reversed by dialysis of the cell interior with Munc-18, a syntaxin-binding protein that typically blocks the interaction of syntaxin with other proteins. Thus, syntaxin 1A cannot inhibit Na(+) permeability in the absence of adequate plasma membrane ASIC2 expression, accounting for the observed functional expression of amiloride-sensitive currents in high grade glioma cells.
Berdiev
Bakhrom K
BK
Department of Physiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Xia
Jiazeng
J
McLean
Lee Anne
LA
Markert
James M
JM
Gillespie
G Yancey
GY
Mapstone
Timothy B
TB
Naren
Anjaparavanda P
AP
Jovov
Biljana
B
Bubien
James K
JK
Ji
Hong-Long
HL
Fuller
Catherine M
CM
Kirk
Kevin L
KL
Benos
Dale J
DJ
D062565:Acid Sensing Ion Channels; D000584:Amiloride / Q000494:pharmacology; D000954:Antigens, Surface / Q000378:metabolism / Q000502:physiology; D001921:Brain / Q000473:pathology; D004252:DNA Mutational Analysis; D053503:Epithelial Sodium Channels; D005910:Glioma / Q000737:chemistry* / Q000235:genetics / Q000473:pathology; D006801:Humans; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009363:Neoplasm Proteins / Q000187:drug effects / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D050827:Syntaxin 1; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000494:pharmacology
C568266:ASIC1 protein, human; C112231:ASIC3 protein, human; D062565:Acid Sensing Ion Channels; D000954:Antigens, Surface; D053503:Epithelial Sodium Channels; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; C494212:STX1A protein, human; D015222:Sodium Channels; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D000584:Amiloride