Molecular Cloning Of PP2A-A And Analysis Of Differential Expression Patterns For Both PP2A-A And PP2A-B In Eye

Protein Phosphorylation and dephosphorylation is a fundamental regulatory mechanism in eukaryotes.Dephosphorylation of protein phosphatases play a critical role in regulating various intracellular processes.Protein phosphatase 2A is one of the critrial serine/threonine phosphatases.Our lab previous studies have established the expression patterns of the catalytic subunit for PP-2A(PP-2Acs)in goldfish and mouse eye.Here,I have got the cDNA clones encoding the alpha and beta isforms of the scaffolding subunit A of PP2A in Goldfish.Then I have investigated the differential expression patterns of the scaffolding subunit A and regulatory subunit B of PP2A in the retina,lens epithelium, lens fiber,and cornea of the goldfish and mouse eye and obtained the following results:(1)Through RACE technology,I have got the cDNA clones encoding the alpha and beta isforms of the scaffolding subunit A of PP2A in Goldfish.The predicted amino acid sequences showed 87.7%and 83.6%identity to other known PP2A-Aαand PP2A-Aβisoforms, respectively.As previously reported for the mammalian PP2A-Aαand PP2A-Aβisoforms,Both goldfish PP2A-Aαand goldfish PP2A-Aβare composed of 15 imperfect repeating units of approximately 38 to 43 amino acids.The residues contributing to this repeat structure show also the highest sequence conservation between species indicating a functional importance for these repeats.It also have offered experiment basis for our further study for the expression of PP2A in goldfish.(2)In goldfish eye,the expression patterns of the scaffold subunits and regulatory subunits of PP2A were analysized at the mRNA,protein and tissue levels in the retina,lens epithelium,lens fiber,and cornea of the goldfish.It was found that the high expression level in retina and coenea of both subunit A and subunit B of PP2A at protein,and low expression level in ocular lens.The mRNA expressions of five isoforms are all different.The results from the localization study on the embryo eyes' development of the fertilized 48-hour goldfish also revealed that high expression level in retina and cornea and the expression level was slightly reduced in ocular lens.(3)In mouse eye,the mouse retina expresses of all five mRNAs for the five isoforms of PP-2A but cornea only three and lens just two;and the proteins for both A and B subunits of PP-2A are highly expressed in retina and cornea but are much less abundant in the lens.The same results have been found in mouse eye tissues.In summary,the genes encoding PP2A-Aa,β,and PP2A-Bα,β,γare all differentially expressed in the four primary tissues of goldfish and mouse eye.These results indicate that the scaffolding subunit A and regulatory subunit B may play important roles in the development of vertebrate eyes.