Prion protein inhibits microtubule assembly by inducing tubulin oligomerization

Prion protein inhibits microtubule assembly by inducing tubulin oligomerization
Received 10 August 2006. Available online 18 August 2006.
Krzysztof Nieznanskia, , , Zoya A. Podlubnayab, c and Hanna Nieznanskaa
Biochemical and Biophysical Research Communications
Volume 349, Issue 1 , 13 October 2006
Copyright ? 2006 Elsevier Inc. All rights reserved.
aNencki Institute of Experimental Biology, Department of Muscle Biochemistry, Warsaw, Poland
bInstitute of Theoretical and Experimental Biophysics, Laboratory of Structure and Function of Muscle Proteins, Pushchino, Russia
cPushchino State University, Pushchino, Russia
A growing body of evidence points to an association of prion protein (PrP) with microtubular cytoskeleton. Recently, direct binding of PrP to tubulin has also been found. In this work, using standard light scattering measurements, sedimentation experiments, and electron microscopy, we show for the first time the effect of a direct interaction between these proteins on tubulin polymerization. We demonstrate that full-length recombinant PrP induces a rapid increase in the turbidity of tubulin diluted below the critical concentration for microtubule assembly. This effect requires magnesium ions and is weakened by NaCl. Moreover, the PrP-induced light scattering structures of tubulin are cold-stable. In preparations of diluted tubulin incubated with PrP, electron microscopy revealed the presence of 50 nm disc-shaped structures not reported so far. These unique tubulin oligomers may form large aggregates. The effect of PrP is more pronounced under the conditions promoting microtubule formation. In these tubulin samples, PrP induces formation of the above oligomers associated with short protofilaments and sheets of protofilaments into aggregates. Noticeably, this is accompanied by a significant reduction of the number and length of microtubules. Hence, we postulate that prion protein may act as an inhibitor of microtubule assembly by inducing formation of stable tubulin oligomers.
Keywords: Prion protein; Tubulin; Microtubules; Oligomerization; Electron microscopy

Abbreviations: CLIP, cytoplasmic linker protein; EB1, end-binding protein 1; GPI, glycosylphosphatidylinositol; GSS, Gerstmann?Str?ussler?Scheinker disease; MAPs, microtubule-associated proteins; MCAK, mitotic centromere-associated kinesin; PrP, prion protein; PrPC, cellular form of prion protein; CtmPrP, transmembrane form of prion protein with the C-terminus residing in the lumen of endoplasmic reticulum; NtmPrP, transmembrane form of prion protein with the N-terminus residing in the lumen of endoplasmic reticulum; PrPSc, scrapie form of prion protein; PrP106?126, peptide corresponding to PrP sequence 106?126; TSE, transmissible spongiform encephalopathy.
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