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2 results on '"Epstein, H F"'

1. Rac-1 and Raf-1 kinases, components of distinct signaling pathways, activate myotonic dystrophy protein kinase

Author

Shimizu, M, Wang, W, Walch, E. T, Dunne, P. W, and Epstein, H. F

Subjects
Life Sciences (General)
Abstract

Myotonic dystrophy protein kinase (DMPK) is a serine-threonine protein kinase encoded by the myotonic dystrophy (DM) locus on human chromosome 19q13.3. It is a close relative of other kinases that interact with members of the Rho family of small GTPases. We show here that the actin cytoskeleton-linked GTPase Rac-1 binds to DMPK, and coexpression of Rac-1 and DMPK activates its transphosphorylation activity in a GTP-sensitive manner. DMPK can also bind Raf-1 kinase, the Ras-activated molecule of the MAP kinase pathway. Purified Raf-1 kinase phosphorylates and activates DMPK. The interaction of DMPK with these distinct signals suggests that it may play a role as a nexus for cross-talk between their respective pathways and may partially explain the remarkable pleiotropy of DM.

Published
2000
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2. Myotonic dystrophy protein kinase phosphorylates the myosin phosphatase targeting subunit and inhibits myosin phosphatase activity.

Author

Murányi A, Zhang R, Liu F, Hirano K, Ito M, Epstein HF, and Hartshorne DJ

Subjects
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine pharmacology, Amides pharmacology, Animals, Base Sequence, Binding Sites, DNA Primers genetics, Enzyme Inhibitors pharmacology, Humans, In Vitro Techniques, Intracellular Signaling Peptides and Proteins, Myosin-Light-Chain Phosphatase, Myotonin-Protein Kinase, Phosphoprotein Phosphatases chemistry, Phosphoprotein Phosphatases metabolism, Phosphorylation, Protein Serine-Threonine Kinases antagonists & inhibitors, Protein Subunits, Pyridines pharmacology, Recombinant Proteins metabolism, rho-Associated Kinases, 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine analogs & derivatives, Myotonic Dystrophy enzymology, Phosphoprotein Phosphatases antagonists & inhibitors, Protein Serine-Threonine Kinases metabolism
Abstract

Myotonic dystrophy protein kinase (DMPK) and Rho-kinase are related. An important function of Rho-kinase is to phosphorylate the myosin-binding subunit of myosin phosphatase (MYPT1) and inhibit phosphatase activity. Experiments were carried out to determine if DMPK could function similarly. MYPT1 was phosphorylated by DMPK. The phosphorylation site(s) was in the C-terminal part of the molecule. DMPK was not inhibited by the Rho-kinase inhibitors, Y-27632 and HA-1077. Several approaches were taken to determine that a major site of phosphorylation was T654. Phosphorylation at T654 inhibited phosphatase activity. Thus both DMPK and Rho-kinase may regulate myosin II phosphorylation.

Published
2001
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