Live-cell imaging reveals divergent intracellular dynamics of polyglutamine disease proteins and supports a sequestration model of pathogenesis

doi:10.1073/pnas.152101299

Live-cell imaging reveals divergent intracellular dynamics of polyglutamine disease proteins and supports a sequestration model of pathogenesis

^*Department of Neurology, 3160 Medical Labs, University of Iowa College of Medicine, Iowa City, IA 52242; and ^†Central Microscopy Research Facility, ^§Medical Scientist Training Program, and ^‡Genetics Graduate Training Program, University of Iowa, Iowa City, IA 52242

Edited by Ronald M. Evans, The Salk Institute for Biological Studies, La Jolla, CA, and approved May 29, 2002 (received for review February 19, 2002)

Abstract

Protein misfolding and aggregation are central features of the polyglutamine neurodegenerative disorders, but the dynamic properties of expanded polyglutamine proteins are poorly understood. Here, we use fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) with green fluorescent protein fusion proteins to study polyglutamine protein kinetics in living cells. Our results reveal markedly divergent mobility states for an expanded polyglutamine protein, ataxin-3, and establish that nuclear inclusions formed by this protein are aggregates. Additional studies of green fluorescent protein-tagged cAMP response element binding protein coexpressed with either of two mutant polyglutamine proteins, ataxin-3 and huntingtin, support a model of disease in which coaggregation of transcriptional components contributes to pathogenesis. Finally, studies of a third polyglutamine disease protein, ataxin-1, reveal unexpected heterogeneity in the dynamics of inclusions formed by different disease proteins, a finding which may help explain disease-specific elements of pathogenesis in these neurodegenerative disorders.

Footnotes

↵ ¶ To whom reprint requests should be addressed. E-mail: henry-paulson{at}uiowa.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

polyQ,

polyglutamine;

NI,

nuclear inclusion;

CBP,

CREB-binding protein;

FRAP,

fluorescence recovery after photobleaching;

FLIP,

fluorescence loss in photobleaching;

GFP,

green fluorescent protein;

CI,

cytoplasmic inclusion