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The characterization of plasma membrane Ca 2+ ‐ATPase in rich sphingomyelin–cholesterol domains
Author(s) -
Pang Yuhong,
Zhu Hua,
Wu Ping,
Chen Jianwen
Publication year - 2005
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2005.03.038
Subject(s) - sphingomyelin , lipid raft , caveolae , sphingolipid , lipid microdomain , chemistry , biophysics , membrane , biochemistry , fluorescence microscope , fluorescence , quenching (fluorescence) , biology , physics , quantum mechanics
According to the raft hypothesis, sphingolipid–cholesterol (CHOL) microdomains are involved in numerous cellular functions. Here, we have prepared liposomes to simulate the lipid composition of rafts/caveolae using phosphatidylchone, sphingomyelin (SPM)–CHOL in vitro. Experiments of both 1,6‐diphenyl‐1,3,5‐hexatriene and merocyanine‐540 fluorescence showed that a phase transition from l d to l o can be observed clearly. In particular, we investigated the behavior of a membrane protein, plasma membrane Ca 2+ ‐ATPase (PMCA), in lipid rafts (l o phase). Three complementary approaches to characterize the physical appearance of PMCA were employed in the present study. Tryptophan intrinsic fluorescence increase, fluorescence quenching by both acrylamid and hypocrellin B decrease, and MIANS fluorescence decrease, indicate that the conformation of PMCA embedded in lipid l o phase is more compact than in lipid l d phase. Also, our results showed that PMCA activity decreased with the increase of SPM–CHOL content, in other words, with the increase of l o phase. This suggests that the specific domains containing high SPM–CHOL concentration are not a favorable place for PMCA activity. Finally, a possible explanation about PMCA molecules concentrated in caveolae/rafts was discussed.