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The Microvascular Effects of Sphingosine Kinase 1 are Regulated by its Subcellular Localization
Author(s) -
Lidington Darcy,
Peter Bernhard Friedrich,
Pitson Stuart,
Pohl Ulrich,
Bolz SteffenSebastian
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a301
Subject(s) - sphingosine kinase 1 , microbiology and biotechnology , phosphorylation , sphingosine , green fluorescent protein , biology , myocyte , vascular smooth muscle , sphingosine 1 phosphate , chemistry , endocrinology , biochemistry , gene , receptor , smooth muscle
Sphingosine kinase 1 (Sk1) is an important regulator of myogenic tone and smooth muscle cell Ca 2+ sensitivity. Phosphorylation of Sk1 at serine 225, which results in its translocation to the plasma membrane, is required for full enzymatic activation. To investigate the functional role of Sk1 phosphorylation and localization, isolated resistance arteries from the hamster gacilis muscle were transfected with GFP or various mutants of Sk1. Elevation of transmural pressure stimulated the translocation of Sk1, but not a non‐phosphorylatable mutant of Sk1 (Sk S225A ). Compared to GFP controls, expression of Sk S225A reduced resting and myogenic tone, resting Ca 2+ , pressure‐induced Ca 2+ elevations and Ca 2+ sensitivity. Inhibition of ERK1/2 signalling (PD98059), which putatively phosphorylates Sk1, had similar effects on resting and myogenic tone. In an attempt to rescue the effects of the S225A mutation, we employed a membrane anchored version of the mutant. Surprisingly, only resting Ca 2+ and pressure‐induced Ca 2+ elevations were restored. Interestingly, expression of a membrane anchored wild‐type Sk1 enzyme also reduced resting tone, myogenic vasoconstriction and Ca 2+ sensitivity compared to GFP controls, but to a lesser extent than the anchored S225A mutant. We conclude that phosphorylation‐dependent translocation of Sk1 to the plasma membrane is critical for its regulatory function in vascular smooth muscle cells. This process can not be imitated by forced localization of Sk1 with a membrane anchor.