How do CMT-related mutations in HSPBl affect its biochemical properties?

[Guest guest]

(Oralll presentation at Antwerpt Consortium July 2009)

How do CMT-related mutations in HSPBl affect its biochemical properties?

L. Almeida-Souza, S. Goethals, A. s, V. De Winter, J. Irobi, V. Timmerman

and S. Janssens

VIB Department of Molecular Genetics, Peripherial Neuropathy Group, University

of Antwerp, Antwerpen, Belgium

Missense mutations in the small heat shock protein HSPB I (Hsp27) were

identified to cause axonal Charcot-Malie-Tooth neuropathy (CMT2F) and distal

hereditary motor neuropathy (distal HMN). Up till now, mutations involving 8

different HSBPI amino acid residues were

shown to be linked to axonal CMT or distal HMN. Small heat shock proteins (sHSP)

act as molecular chaperones and confer stress resistance to different cells

types.

They bind to unfolded proteins and keep them in a folding competent

state. The refolding of the sHSP-bound proteins is subsequently mediated by the

ATPdependent chaperones HSP70 and HSP90 sHSPs present themselves in cells in a

dynamic equiliblium flam monomeric to oligomeric forms. These states are

regulated by phosphorylation, and stress conditions tend to dislocate this

equilibrium to

monomeric/dimeric forms, which are described as the binding-active states of

these proteins.

We decided to study whether the distal HMN and axonal CMT related HSPBI

mutations have any effect on the basic biochemical properties of this protein.

Making use of stably expressing neuronal cell lines, we tested the in vivo

chaperone activity, the thermotolerance,

oligomeric size and phosphorylation state of 5 selected HSPBI mutations (RI27W,

S135F, R136W, Tl51I and P182L) and wild type protein.

Our results show that these mutations differentially affect the HSPB I

biochemical properties. These data suggest that the different

HSPBI mutations might cause CMT through different pathomechanisms.