Investigating the involvement of the immunophilin FKBP12 in the neurochemical pathology of Alzheimer's disease brain

Abstract

The immunophilin FKBP12 (FK506 Binding Rotcin, M.W. 12kDa) is expressed to high levels in brain where it plays a role in neuroprotdon and neuroregeneration. This protein also interfaces with and regulates the function of the ryanodine and inositol 1,4,5-triphosphate receptors and colocalises with calcinewin, all of which arc dysfunctional in Alzheimer's disease (AD). To examine the functional integrity of FKBPl2 in AD, the present study examined FKBP12 levels and [3H]FK506 binding in pathologically a f f d and unaffected areas of matched AD and control post mortem brain. Western immunoblotting analysis of soluble fractions detsdad a single immuwnaCtive band (14kDa) d g r a t i n g with pure human recombinant FKBP12. A significant and selective (P<o.OOl) -40% reduction in FKBPl2 levels was detected in AD tempual cortex soluble fractions compared to controls but not in the putamen or cnebellar fractions. We also detected a significant reduction in FKBPl2 levels in the same samples where the related @culate fractions exhibit a significant reduction in [3H]ryanodine binding. We had anticipated that Bmax values for [%]FK506 would also be reduced in AD soluble fractions in the presence of -40% less FKBP12. as FKBP12 is the major binding protein and effector molecule for FK506.However, this was not the case and a single hi& afiinity binding site with similar KD and Bmax, values was deteaed in both groups. Overall these results describing reduced levels and functional differences in FKBPl2 unique to pathologically affected areas in AD brain would be hypothesised to affect the diverse signalling function of this protein and may date to AD pathogenesis. Supponed by theHealth RcscarchBoard oflrrledWe would also like to thpnk Fujtaawa GmbH for chc ~+ncrous ,gift of FK506.