Dynamic regulation of a cell adhesion protein complex including CADM1 by combinatorial analysis of FRAP with exponential curve-fitting

PLoS One. 2015 Mar 17;10(3):e0116637. doi: 10.1371/journal.pone.0116637. eCollection 2015.

Abstract

Protein components of cell adhesion machinery show continuous renewal even in the static state of epithelial cells and participate in the formation and maintenance of normal epithelial architecture and tumor suppression. CADM1 is a tumor suppressor belonging to the immunoglobulin superfamily of cell adhesion molecule and forms a cell adhesion complex with an actin-binding protein, 4.1B, and a scaffold protein, MPP3, in the cytoplasm. Here, we investigate dynamic regulation of the CADM1-4.1B-MPP3 complex in mature cell adhesion by fluorescence recovery after photobleaching (FRAP) analysis. Traditional FRAP analysis were performed for relatively short period of around 10 min. Here, thanks to recent advances in the sensitive laser detector systems, we examine FRAP of CADM1 complex for longer period of 60 min and analyze the recovery with exponential curve-fitting to distinguish the fractions with different diffusion constants. This approach reveals that the fluorescence recovery of CADM1 is fitted to a single exponential function with a time constant (τ) of approximately 16 min, whereas 4.1B and MPP3 are fitted to a double exponential function with two τs of approximately 40-60 sec and 16 min. The longer τ is similar to that of CADM1, suggesting that 4.1B and MPP3 have two distinct fractions, one forming a complex with CADM1 and the other present as a free pool. Fluorescence loss in photobleaching analysis supports the presence of a free pool of these proteins near the plasma membrane. Furthermore, double exponential fitting makes it possible to estimate the ratio of 4.1B and MPP3 present as a free pool and as a complex with CADM1 as approximately 3:2 and 3:1, respectively. Our analyses reveal a central role of CADM1 in stabilizing the complex with 4.1B and MPP3 and provide insight in the dynamics of adhesion complex formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Cell Adhesion
  • Cell Adhesion Molecule-1
  • Cell Adhesion Molecules / metabolism*
  • Dogs
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism
  • Fluorescence Recovery After Photobleaching*
  • Humans
  • Immunoglobulins / metabolism*
  • Kinetics
  • Madin Darby Canine Kidney Cells
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / metabolism*
  • Movement
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism*
  • Protein Stability
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*

Substances

  • CADM1 protein, human
  • Cell Adhesion Molecule-1
  • Cell Adhesion Molecules
  • DLG3 protein, human
  • EPB41L3 protein, human
  • Immunoglobulins
  • Microfilament Proteins
  • Nuclear Proteins
  • Transcription Factors

Grants and funding

A CREST project from Japan Science and Technology Agency [M. S. -Y., T. S., K. I., Y. M.]; a Grant-in-Aid for Scientific Research (B) [25290051 for Y. M.] and a Grant-in-Aid for Young Scientists (B) [24790310 for M. S. -Y.] from the Ministry of Education, Culture, Sports, Science, and Technology, Japan; a Grant-in-Aid for the Third Term Comprehensive Control Research for Cancer from the Ministry of Health, Labor, and Welfare, Japan [22090601 and 23120701 for Y. M.]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.