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PKC decodes Ca²⁺

Ca2+ waves are read out as waves of PKC translocation to the plasma membrane (shown).

Movements of a swift kinase keep up with quick calcium bursts, based on findings of Reither et al. (page 521).

Cellular Ca²⁺ signals come in many flavors—from long-lasting global increases to waves to brief local plumes. Each flavor is translated into a specific cellular response by Ca²⁺ sensors, including calmodulin and conventional PKCs (cPKCs).

Upon Ca²⁺ binding, PKC—a common cPKC—translocates to the plasma membrane, the location of most of its targets, including ion channels and transporters. The bulkiness of PKC might suggest that its diffusion constants should be too low for rapidly following the fast and brief Ca²⁺ signals. Many researchers thus suspected that tiny calmodulin must be the main translator of these signals.

But the new findings reveal that PKC is fleet footed. The authors found that PKC's membrane translocation mimics—in both space and time—the full range of the cellular Ca²⁺ signals.

Just fractions of a second after a Ca²⁺ burst, PKC was found at the membrane, where it lingered either for mere milliseconds or for longer stretches of several seconds. The short-lived membrane residence solely depended on cytosolic Ca²⁺. The more intimate interactions required PKC's binding to the membrane lipid diacylglycerol (DAG). Since this binding is required for full activation of the kinase, the authors suspect that the shorter interactions might not necessarily lead to downstream signaling events.

Copies of PKC that encounter Ca²⁺ in the center of the cell are unlikely ever to make it to the plasma membrane, as the Ca²⁺-PKC complex is short lived. The authors thus suggest that PKC activation depends solely on sub–plasma membrane Ca²⁺ signals. Perinuclear signals probably trigger an entirely different set of downstream events—perhaps via calmodulin, which has many cytoplasmic substrates.

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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This Article Full Text (PDF, 1286K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Social Bookmarking                            What's this?