Mutation-dependent aggregation of tau protein and its selective depletion from the soluble fraction in brain of P301L FTDP-17 patients.
Mutations in the gene for the microtubule-associated protein tau are associated with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). In this study we compared the presence of the P301L mutated tau protein from brain material of patients with that of the normal 4-repeat, using polyclonal antibodies specific for the P301L point mutation and its normal counterpart. We determined the relative ratio of mutated versus normal tau protein in the sarkosyl-soluble and -insoluble protein fractions from several brain regions. Although mutated and normal tau proteins are both present in the sarkosyl-insoluble deposits, quantitative analysis showed that the mutated protein is the major component. In the sarkosyl-soluble fraction of frontal and temporal cortex the overall ratio of 3-repeat versus 4-repeat tau isoforms is unchanged but there is a dramatic depletion of mutant tau protein. Furthermore, we observed an increase in tau-immunoreactive cleavage products with the P301L antibody, suggesting that the mutant protein is partly resistant to degradation and this is confirmed by pulse-chase experiments. This is the first direct evidence using patient material that shows a selective aggregation of mutant tau protein resulting in sarkosyl-insoluble deposits and the specific depletion of mutated tau protein in the soluble fraction.
Rizzu
P
P
Department of Clinical Genetics, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
Joosse
M
M
Ravid
R
R
Hoogeveen
A
A
Kamphorst
W
W
van Swieten
J C
JC
Willemsen
R
R
Heutink
P
P
D000368:Aged; D019943:Amino Acid Substitution; D000818:Animals; D000906:Antibodies; D019556:COS Cells; D002540:Cerebral Cortex / Q000378:metabolism*; D002886:Chromosomes, Human, Pair 17; D003704:Dementia / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000276:immunology; D008875:Middle Aged; D016716:PC12 Cells; D020734:Parkinsonian Disorders / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D017397:Prefrontal Cortex / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D016875:tau Proteins / Q000235:genetics* / Q000276:immunology
D000906:Antibodies; C054369:MAPT protein, human; D008869:Microtubule-Associated Proteins; D016875:tau Proteins