Stimulation of strontium accumulation in linoleate-enriched Saccharomyces cerevisiae is a result of reduced Sr2+ efflux.
The influence of modified plasma membrane fatty acid composition on cellular strontium accumulation in Saccharomyces cerevisiae was investigated. Growth of S. cerevisiae in the presence of 1 mM linoleate (18:2) (which results in 18:2 incorporation to approximately 70% of total cellular and plasma membrane fatty acids, with no effect on growth rate) yielded cells that accumulated Sr2+ intracellularly at approximately twice the rate of S. cerevisiae grown without a fatty acid supplement. This effect was evident over a wide range of external Sr2+ concentrations (25 microM to 5 mM) and increased with the extent of cellular 18:2 incorporation. Stimulation of Sr2+ accumulation was not evident following enrichment of S. cerevisiae with either palmitoleate (16:1), linolenate (18:3) (n-3 and n-6 isomers), or eicosadienoate (20:2) (n-6 and n-9 isomers). Competition experiments revealed that Ca2+- and Mg2+-induced inhibition of Sr2+ accumulation did not differ between unsupplemented and 18:2-supplemented cells. Treatment with trifluoperazine (TFP) (which can act as a calmodulin antagonist and Ca2+-ATPase inhibitor), at a low concentration that precluded nonspecific K+ efflux, increased intracellular Sr2+ accumulation by approximately 3.6- and 1.4-fold in unsupplemented and 18:2-supplemented cells, respectively. Thus, TFP abolished the enhanced Sr2+ accumulation ability of 18:2-supplemented cells. Moreover, the rate of Sr2+ release from Sr2+-loaded fatty acid-unsupplemented cells was found to be at least twice as great as that from Sr2+-loaded 18:2-enriched cells. The influence of enrichment with other fatty acids on Sr2+ efflux was variable. The results reveal an enhanced Sr2+ accumulation ability of S. cerevisiae following 18:2-enrichment, which is attributed to diminished Sr2+ efflux activity in these cells.
Avery
S V
SV
Department of Biology, University Plaza, Georgia State University, Atlanta, Georgia 30302-4010, USA. biosva@panther.gsu.edu
Smith
S L
SL
Ghazi
A M
AM
Hoptroff
M J
MJ
D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry*; D002463:Cell Membrane Permeability; D003470:Culture Media; D005227:Fatty Acids / Q000032:analysis; D019787:Linoleic Acid / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D013324:Strontium / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D003470:Culture Media; D005227:Fatty Acids; D014268:Trifluoperazine; D019787:Linoleic Acid; D008274:Magnesium; D002118:Calcium; D013324:Strontium