IngentaConnect Neuroserpin Portland (Ser52Arg) is trapped as an inactive interme...

Authors: Belorgey, Didier¹; Sharp, Lynda K.¹; Crowther, Damian C.¹; Onda, Maki²; Johansson, Jan³; Lomas, David A.¹

Source: FEBS Journal, Volume 271, Number 16, August 2004 , pp. 3360-3367(8)

Abstract:

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 β-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 β-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 mutant may result in uncontrolled activity of tissue plasminogen activator, and so explain the epileptic seizures seen in individuals with more severe forms of the disease.

Keywords: conformational diseases; neuroserpin; polymerization; serpin; serpinopathies

Document Type: Research article

DOI: 10.1111/j.1432-1033.2004.04270.x

Affiliations: 1: Cambridge Institute for Medical Research, Department of Medicine, University of Cambridge, UK 2: Department of Environmental Sciences, Faculty of Science, Osaka Women's University, Sakai, Japan 3: Department of Molecular Biosciences, Swedish University of Agricultural Sciences, Uppsala, Sweden

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Neuroserpin Portland (Ser52Arg) is trapped as an inactive intermediate that rapidly forms polymers: Implications for the epilepsy seen in the dementia FENIB