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A more recent version of this article appeared on July 1, 2007
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Submitted on December 13, 2006
Revised on April 19, 2007
Accepted on May 3, 2007
*Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;
Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas-Universidad Autónoma, Facultad de Ciencias, Cantoblanco, Universidad Autónoma de Madrid, 28049 Madrid, Spain;
Fundación Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain
Monitoring Editor: Asma Nusrat
In this manuscript we analyze the mechanisms by which the C-terminal four amino acids of NOS2 interact with proteins that contain PDZ domains resulting in the translocation of NOS2 to the cellular apical domain. It has been reported that human hepatic NOS2 associates to EBP50, a protein with two PDZ domains present in epithelial cells. We describe herein that NOS2 binds through its four carboxy-terminal residues to CAP70, a protein that contains four PDZ modules that is targeted to apical membranes. Interestingly, this interaction augments both the cytochrome c reductase and ·NO-synthase activities of NOS2. Binding of CAP70 to NOS2 also results in an increase in the population of active NOS2 dimers. In addition, CAP70 participates in the correct subcellular targeting of NOS2 in a process that is also dependent on the acylation state of the N-terminus end of NOS2. Hence, nonpalmitoylated NOS2 is unable to progress toward the apical side of the cell despite its interaction with either EBP50 or CAP70. Likewise, if we abrogate the interaction of NOS2 with either EBP50 or CAP70 by fusing the GFP reporter to the carboxy-terminus end of NOS2 palmitoylation is not sufficient to confer an apical targeting.