Latent S49P Neuroserpin Forms Polymers in the Dementia Familial Encephalopathy with Neuroserpin Inclusion Bodies

David A. Lomas,Didier Belorgey,Lynda K. Sharp,Maki Onda

doi:10.1074/jbc.m413282200

Abstract

The serpinopathies result from conformational transitions in members of the serine proteinase inhibitor superfamily with aberrant tissue deposition or loss of function. They are typified by mutants of neuroserpin that are retained within the endoplasmic reticulum of neurons as ordered polymers in association with dementia. We show here that the S49P mutant of neuroserpin that causes the dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) forms a latent species in vitro and in vivo in addition to the formation of polymers. Latent neuroserpin is thermostable and inactive as a proteinase inhibitor, but activity can be restored by refolding. Strikingly, latent S49P neuroserpin is unlike any other latent serine proteinase inhibitor (serpin) in that it spontaneously forms polymers under physiological conditions. These data provide an alternative method for the inactivation of mutant neuroserpin as a proteinase inhibitor in FENIB and demonstrate a second pathway for the formation of intracellular polymers in association with disease.

Highlights

Neuroserpin is a member of the serine proteinase inhibitor1 superfamily that is predominantly expressed by neurons in the developing and adult brain
We show here that the S49P mutant of neuroserpin that causes the dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) forms a latent species in vitro and in vivo in addition to the formation of polymers
It is secreted from the axonal growth cones of the central and peripheral nervous system, where it inhibits the enzyme tissue plasminogen activator [1,2,3,4,5]

Summary

Introduction

Neuroserpin is a member of the serine proteinase inhibitor (serpin)1 superfamily that is predominantly expressed by neurons in the developing and adult brain. We show here that the S49P mutant of neuroserpin that causes the dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) forms a latent species in vitro and in vivo in addition to the formation of polymers. Latent S49P neuroserpin is unlike any other latent serine proteinase inhibitor (serpin) in that it spontaneously forms polymers under physiological conditions.

Results

Conclusion