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The dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) is caused by point mutations in the neuroserpin gene.We have shown a correlation between the predicted effect of the mutation and the number of intracerebral inclusions, and an inverse relationshipwith the age of onset of disease. Our previous work has shown that the intraneuronal inclusions in FENIB result from the sequential interactionbetween the reactive centre loopofone neuroserpin molecule withb-sheet A of the next. . | Eur. J. Biochem. 271 3360-3367 2004 FEBS 2004 doi 10.1111 j.1432-1033.2004.04270.x Neuroserpin Portland Ser52Arg is trapped as an inactive intermediate that rapidly forms polymers Implications for the epilepsy seen in the dementia FENIB Didier Belorgey1 Lynda K. Sharp1 Damian C. Crowther1 Maki Onda2 Jan Johansson3 and David A. Lomas1 1 Cambridge Institute for Medical Research Department of Medicine University of Cambridge UK 2Department of Environmental Sciences Faculty of Science Osaka Women s University Sakai Japan 3Department of Molecular Biosciences Swedish University of Agricultural Sciences Uppsala Sweden The dementia familial encephalopathy with neuroserpin inclusion bodies FENIB is caused by point mutations in the neuroserpin gene. We have shown a correlation between the predicted effect of the mutation and the number of intracerebral inclusions and an inverse relationship with the age of onset of disease. Our previous work has shown that the intraneuronal inclusions in FENIB result from the sequential interaction between the reactive centre loop of one neuroserpin molecule with b-sheet A of the next. We show here that neuroserpin Portland Ser52Arg which causes a severe form of FENIB also forms loop-sheet polymers but at a faster rate in keeping with the more severe clinical phenotype. The Portland mutant has a normal unfolding transition in urea and a normal melting temperature but is inactive as a proteinase inhibitor. This results in part from the reactive loop being in a less accessible conformation to bind to the target enzyme tissue plasminogen activator. These results with those of the CD analysis are in keeping with the reactive centre loop of neuroserpin Portland being partially inserted into b-sheet A to adopt a conformation similar to an intermediate on the polymerization pathway. Our data provide an explanation for the number of inclusions and the severity of dementia in FENIB associated with neuroserpin Portland. Moreover the inactivity of the
