Developmentally expressed myosin heavy‐chain kinase possesses a diacylglycerol kinase domain

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Abstract
In Dictyostelium, an ordered actin and myosin assembly‐disassembly process is necessary for proper development, differentiation, and motility (Yumura S, Fukui F, 1985, Nature 314(6007): 194–196; Ravid S, Spudich JA, 1989, J Biol Chem 264(25): 15144–15150), and phosphorylation of myosin heavy chains has been implicated in the myosin assembly‐disassembly process (Egelhoff TT, Lee RJ, Spudich JA, 1993, Cell 75(2):363–371). The developmentally expressed 84‐kDa myosin heavy‐chain kinase (MHCK) from Dictyostelium (Ravid S, Spudich JA, 1992, Proc Natl Acad Sci USA 89(13):5877–5881) is known to be a member of the protein kinase C (PKC) family. We have observed a rather striking homology between the large central domain of MHCK and the catalytic domain of diacylglycerol kinase (DGK), indicating that MHCK is in fact a gene fusion between a DGK and a PKC, possessing two separate kinase domains. The combined diacylglycerol kinase/myosin heavy‐chain kinase (DGK/MHCK) may therefore have dual functionality, possessing the ability to phosphorylate both protein and lipid. We present a hypothesis that DGK/MHCK can antagonize both actin and myosin assembly, as well as other cellular processes, by coordinated down regulation of signaling via myosin heavy‐chain kinase activity and diacylglycerol kinase activity.
Funding Information
  • Pew Charitable Trusts and the National Science Foundation
  • National Institutes of Health