The latch region of calcineurin B is involved in both immunosuppressant-immunophilin complex docking and phosphatase activation.
The immunosuppressants cyclosporin A and FK506, when complexed with their intracellular receptors, prevent T cell activation by directly binding to the phosphatase calcineurin. We have used molecular modeling and mutagenesis to identify sites on calcineurin important for this interaction. We have created calcineurins that are resistant to both cyclosporin A and FK506 by mutating specific residues in CnB, a calcium-binding protein that regulates the catalytic subunit, CnA. Significantly, on a model of CnB, these mutations map to the latch region, an element of tertiary structure that forms when CnB binds CnA. In addition, we show that this latch region plays an important role in activating the catalytic subunit CnA. These results suggest a molecular mechanism for suppression of calcineurin by cyclosporin A and FK506 involving their binding to the same region of CnB used for allosterically activating CnA.
Milan
D
D
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.
Griffith
J
J
Su
M
M
Price
E R
ER
McKeon
F
F
D000591:Amino Acid Isomerases / Q000378:metabolism; D019703:Calcineurin; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D016572:Cyclosporine / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004351:Drug Resistance / Q000235:genetics; D004789:Enzyme Activation; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008213:Lymphocyte Activation / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D019696:Peptidylprolyl Isomerase; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis; D015398:Signal Transduction / Q000502:physiology; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000502:physiology; D016559:Tacrolimus / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins
D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D016572:Cyclosporine; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000591:Amino Acid Isomerases; D022021:Tacrolimus Binding Proteins; D019696:Peptidylprolyl Isomerase; D002118:Calcium; D016559:Tacrolimus