Localization and kinetics of protein kinase C-epsilon anchoring in cardiac myocytes

Biophys J. 2001 May;80(5):2140-51. doi: 10.1016/S0006-3495(01)76187-5.

Abstract

Protein kinase C-epsilon (PKC-epsilon) plays a central role in cardiac cell signaling, but mechanisms of translocation and anchoring upon activation are poorly understood. Conventional PKC isoforms rely on a rapid Ca2+-mediated recruitment to cell membranes, but this mechanism cannot be employed by PKC-epsilon or other PKC isoforms lacking a Ca2+-binding domain. In this study, we used recombinant green fluorescent protein (GFP) fusion constructs and confocal microscopy to examine the localization, kinetics, and reversibility of PKC-epsilon anchoring in permeabilized rat cardiac myocytes. PKC-epsilon-GFP bound with a striated pattern that co-localized with alpha-actinin, a marker of the Z-line of the sarcomere. Binding required activation of PKC and occurred slowly but reversibly with apparent rate constants of k(on) = 4.6 +/- 1.2 x 10(3) M(-1) x s(-1) and k(off) = 1.4 +/- 0.5 x 10(-3) s(-1) (t1/2 = 8 min) as determined by fluorescence recovery after photobleaching and by perfusion experiments. A truncated construct composed of the N-terminal 144-amino-acid variable region of PKC-epsilon (epsilonV1-GFP), but not an analogous N-terminal domain of PKC-delta, mimicked the Z-line decoration and slow binding rate of the full-length enzyme. These findings suggest that the epsilonV1 domain is important in determining PKC-epsilon localization and translocation kinetics in cardiac muscle. Moreover, PKC-epsilon translocation is not a diffusion-controlled binding process but instead may be limited by intramolecular conformational changes within the V1 domain. The k(off) for epsilonV1-GFP was two- to threefold faster than for full-length enzyme, indicating that other domains in PKC-epsilon contribute to anchoring by prolonging the bound state.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Brain / metabolism
  • Calcium / metabolism
  • Cells, Cultured
  • DNA, Complementary / metabolism
  • Dose-Response Relationship, Drug
  • Gene Library
  • Green Fluorescent Proteins
  • Isoenzymes / biosynthesis*
  • Isoenzymes / chemistry*
  • Kinetics
  • Luminescent Proteins / metabolism
  • Mice
  • Microscopy, Confocal
  • Myocardium / cytology*
  • Myocardium / enzymology*
  • Perfusion
  • Protein Binding
  • Protein Isoforms
  • Protein Kinase C / biosynthesis*
  • Protein Kinase C / chemistry*
  • Protein Kinase C-epsilon
  • Protein Structure, Tertiary
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Fusion Proteins / metabolism
  • Time Factors

Substances

  • DNA, Complementary
  • Isoenzymes
  • Luminescent Proteins
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Prkce protein, mouse
  • Prkce protein, rat
  • Protein Kinase C
  • Protein Kinase C-epsilon
  • Calcium