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JFC1, a novel tandem C2 domain-containing protein associated with the leukocyte NADPH oxidase

J K McAdara Berkowitz1, S D Catz, J L Johnson

  • 1Department of Molecular and Experimental Medicine, Division of Biochemistry, The Scripps Research Institute, La Jolla, California 92037, USA.

The Journal of Biological Chemistry
|March 30, 2001
PubMed

Insights

Researchers identified JFC1, a novel protein that acts as an adaptor in the NADPH oxidase complex. JFC1 links phosphatidylinositol 3-kinase products to the cytosolic components, regulating its function.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The NADPH oxidase is a crucial enzyme complex involved in cellular defense mechanisms.
  • Understanding the regulatory components of NADPH oxidase is essential for elucidating its function in various cell types.
  • p67(phox) is a key regulatory subunit of the NADPH oxidase complex.

Purpose of the Study:

  • To identify novel regulatory components of the NADPH oxidase complex.
  • To characterize the function and binding interactions of a newly discovered protein, JFC1.
  • To investigate the role of JFC1 in the assembly and regulation of the NADPH oxidase.

Main Methods:

  • Yeast two-hybrid system screening of a B lymphoblast cDNA library.
  • Affinity chromatography to confirm protein-protein interactions.
  • Analysis of protein expression and localization in neutrophils.
  • Binding assays using recombinant proteins and lipid substrates.

Main Results:

  • A novel human protein, JFC1 (62 kDa), was identified and cloned.
  • JFC1 contains tandem C2 domains, with C2A showing homology to synaptotagmins.
  • JFC1 mRNA is highly expressed in bone marrow and leukocytes, localizing to the plasma membrane/secretory vesicle fraction in neutrophils.
  • JFC1 directly binds to p67(phox), an essential component of the NADPH oxidase cytosolic complex.
  • JFC1 binds to phosphatidylinositol 3,4,5-trisphosphate and phosphatidylinositol 3,4-diphosphate, but not inositol 1,3,4,5-tetrakisphosphate.

Conclusions:

  • JFC1 functions as an adaptor protein, bridging phosphatidylinositol 3-kinase products to the NADPH oxidase cytosolic complex.
  • This interaction mediated by JFC1 is critical for the proper assembly and activation of the NADPH oxidase.
  • JFC1 represents a novel regulatory element in the NADPH oxidase signaling pathway, with potential implications in immune cell function.

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