title: Microtubule-associated protein tau in bovine retinal photoreceptor rod outer segments: comparison with brain tau.
abstract: Recent studies have suggested a possible involvement of abnormal tau in some retinal degenerative diseases. The common view in these studies is that these retinal diseases share the mechanism of tau-mediated degenerative diseases in brain and that information about these brain diseases may be directly applied to explain these retinal diseases. Here we collectively examine this view by revealing three basic characteristics of tau in the rod outer segment (ROS) of bovine retinal photoreceptors, i.e., its isoforms, its phosphorylation mode and its interaction with microtubules, and by comparing them with those of brain tau. We find that ROS contains at least four isoforms: three are identical to those in brain and one is unique in ROS. All ROS isoforms, like brain isoforms, are modified with multiple phosphate molecules; however, ROS isoforms show their own specific phosphorylation pattern, and these phosphorylation patterns appear not to be identical to those of brain tau. Interestingly, some ROS isoforms, under the normal conditions, are phosphorylated at the sites identical to those in Alzheimer's patient isoforms. Surprisingly, a large portion of ROS isoforms tightly associates with a membranous component(s) other than microtubules, and this association is independent of their phosphorylation states. These observations strongly suggest that tau plays various roles in ROS and that some of these functions may not be comparable to those of brain tau. We believe that knowledge about tau in the entire retinal network and/or its individual cells are also essential for elucidation of tau-mediated retinal diseases, if any.
authors.affiliation: Department of Ophthalmology and Pharmacology, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Akio
authors.initials: A
authors.lastname: Yamazaki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishizawa
authors.forename: Isao
authors.initials: I
authors.lastname: Matsuura
authors.forename: Fumio
authors.initials: F
authors.lastname: Hayashi
authors.forename: Jiro
authors.initials: J
authors.lastname: Usukura
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Bondarenko
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D015180:Electrophoresis, Gel, Two-Dimensional; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D055214:Retinal Photoreceptor Cell Outer Segment / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D016875:tau Proteins
keywords: AD; AP; Alzheimer's disease; BSA; Cdk5; DTT; FTDP-17; MT; MW; Microtubule-associated proteins; Neurodegenerative diseases; PDE; PHF; PMSF; Pγ; ROS; Retinal degenerative diseases; Tau; Tα; alkaline phosphatase; bovine serum albumin; cGMP phosphodiesterase; cyclin-dependent protein kinase 5; dithiothreitol; front-temporal dementia with parkinsonism liked to chromosome; isoelectric point; microtubule; molecular weight; pI; paired helical filament; phenylmethylsulfonyl fluoride; rod outer segments of retinal photoreceptors; the inhibitory subunit of cGMP phosphodiesterase; the α subunit of retinal G protein