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Effects of polyamines and calcium and sodium ions on smooth muscle cytoskeleton‐associated phosphatidylinositol (4)‐phosphate 5‐kinase
Author(s) -
Chen H.,
Baron C. B.,
Griffiths T.,
Greeley P.,
Coburn R. F.
Publication year - 1998
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199810)177:1<161::aid-jcp17>3.0.co;2-g
Subject(s) - phosphatidylinositol , spermine , phosphatidylinositol 4,5 bisphosphate , biochemistry , inositol , phospholipase c , kinase , chemistry , diacylglycerol kinase , biology , microbiology and biotechnology , protein kinase c , enzyme , receptor
In many different cell types, including smooth muscle cells (Baron et al., 1989, Am. J. Physiol., 256: C375–383; Baron et al., J. Pharmacol. Exp. Ther. 266: 8–15), phosphatidylinositol (4)‐phosphate 5‐kinase plays a critical role in the regulation of membrane concentrations of phosphatidylinositol (4,5)‐bisphosphate and formation of inositol (1,4,5)‐trisphosphate. In unstimulated porcine trachealis smooth muscle, 70% of total cellular phosphatidylinositol (4)‐phosphate 5‐kinase activity was associated with cytoskeletal proteins and only trace activity was detectable in isolated sarcolemma. Using two different preparations, we studied cytoskeleton‐associated phosphatidylinositol (4)‐phosphate 5‐kinase under conditions that attempted to mimic the ionic and thermal cytoplasmic environment of living cells. The cytoskeleton‐associated enzyme, studied using phosphatidylinositol (4)‐phosphate substrate concentrations that produced phosphatidylinositol 4,5‐bisphosphate at about 10% of the maximal rate, was sensitive to free [Mg 2+ ], had an absolute requirement for phosphatidylserine, phosphatidic acid, or phosphatidylinositol, and included type I isoforms. At 0.5 mM free [Mg 2+ ], physiological spermine concentrations, 0.2–0.4 mM, increased phosphatidylinositol (4)‐phosphate 5‐kinase activity two to four times compared to controls run without spermine. The EC 50 for spermine‐evoked increases in activity was 0.17 ± 0.02 mM. Spermine‐evoked enzyme activity was a function of both free [Mg 2+ ] and substrate concentration. Cytoskeleton‐associated phosphatidylinositol (4)‐phosphate 5‐kinase was inhibited by free [Ca 2+ ] over a physiological range for cytoplasm − 10 −8 to 10 −5 M, an effect independent of the presence of calmodulin. Na + over the range 20 to 50 mM also inhibited this enzyme activated by 5 mM Mg 2+ but had no effect on spermine‐activated enzyme. Na + , Ca 2+ , and spermine appear to be physiological modulators of smooth muscle cytoskeleton‐bound phosphatidylinositol (4)‐phosphate 5‐kinase. J. Cell. Physiol. 177:161–173, 1998. © 1998 Wiley‐Liss, Inc.