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Dallas P. Seitz, Mohammed Khysar Pasha, Baljit Singh, Audrey Chu, Rajendra K. Sharma; Localization and Characterization of Calcineurin in Bovine Eye. Invest. Ophthalmol. Vis. Sci. 2002;43(1):15-21.
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purpose. There are several aspects of the visual system that may be regulated by
Ca2+- and calmodulin (CaM)-stimulated protein phosphatase.
In the present study, the distribution and characterization of
calcineurin (CaN) in bovine eye was determined.
methods. Whole bovine eyes were either homogenized for purification or
regionally dissected to determine CaN localization and activity.
Dissected tissues were homogenized and Western blot analysis performed,
using polyclonal anti-CaN antibodies, and assayed using p-nitrophenyl phosphate (PNPP) as a substrate to
determine the dephosphorylation activity of CaN. Fresh samples were
then prepared for immunohistochemistry and probed with polyclonal
results. CaN was found to be present in all eye tissues, although activity and
protein expression varied. The highest levels of CaN activity and
protein expression were found in the optic nerve, retina, and cornea.
Immunohistochemical methods displayed similar results with additional
staining of the optic nerve vasculature. Assays of purified CaN
demonstrated that bovine eye CaN had regulatory properties similar to
CaN isolated from other tissues. Probing eye tissues with CaN A
isoform-specific antibodies demonstrated that eye tissues displayed
variable distributions of the CaN Aα and CaN Aβ isoforms.
conclusions. The presence of CaN in the bovine eye provides a physiological pathway
by which the phosphorylated state of proteins and intracellular
Ca2+ concentrations can be coordinated. The authors propose
that CaN is involved in the immunologic privilege of the cornea,
retinal signal transduction, and the toxic effects of
immunosuppressants on the eye. Further in vivo studies of CaN function
are necessary to understand the contributions of CaN to ocular
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