An altered phosphoprotein in cystic fibrosis.

Phosphorylation of calmodulin-dependent regulator proteins has been studied in control and CF submandibular glands. Results showed that a 61,000 molecular weight calmodulin-binding protein was less phosphorylated in CF glands than control (p less than 0.001 for difference). The altered calmodulin-binding protein cross-reacted with an antiserum against a known calmodulin-dependent protein phosphatase, calcineurin. An alteration in a protein with calcineurin-like activity in CF epithelial cells would provide a link between defective beta-adrenergic responses and altered Ca2(+)-mediated events in CF and thus might be directly related to the genetic defect.