Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 276, Issue 15, Pages 12182-12189Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M010056200
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- NCI NIH HHS [T32CA75926] Funding Source: Medline
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Human calmodulin-like protein (CLP) is an epithelial-specific Ca2+-binding protein whose expression is strongly down-regulated in cancers. Like calmodulin, CLP is thought to regulate cellular processes via Ca2+-dependent interactions with specific target proteins. Using gel overlays, we identified a similar to 210-kDa protein binding specifically and in a Ca2+-dependent manner to CLP, but not to calmodulin. Yeast two-hybrid screening yielded a CLP-interacting clone encoding the three light chain binding IQ motifs of human unconventional myosin X. Pull-down experiments showed CLP binding to the IQ domain to be direct and Ca2+-dependent. CLP interacted strongly with IQ motif 3 (K-d similar to0.5 nM) as determined by surface plasmon resonance. Epitope-tagged myosin X was localized preferentially at the cell periphery in MCF-7 cells, and CLP colocalized with myosin X in these cells. Myosin X was able to coprecipitate CLP and, to a lesser extent, calmodulin from transfected COS-1 cells, indicating that CLP is a specific light chain of myosin X in vivo. Because unconventional myosins participate in cellular processes ranging from membrane trafficking to signaling and cell motility, myosin X is an attractive CLP target. Altered myosin X regulation in (tumor) cells lacking CLP may have as yet unknown consequences for cell growth and differentiation.
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