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Vol. 19, Issue 10, 4521-4533, October 2008
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, but with Consequences for Filament Organization and
B-Crystallin Association


*School of Biological and Biomedical Sciences, The University of Durham, Durham DH1 3LE, United Kingdom; and
Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, 1105 BA Amsterdam, The Netherlands
Submitted March 14, 2008;
Revised July 8, 2008;
Accepted July 30, 2008
Monitoring Editor: Thomas D. Pollard
The glial fibrillary acidic protein (GFAP) gene is alternatively spliced to give GFAP-
, the most abundant isoform, and seven other differentially expressed transcripts including GFAP-
. GFAP-
has an altered C-terminal domain that renders it incapable of self-assembly in vitro. When titrated with GFAP-
, assembly was restored providing GFAP-
levels were kept low (
10%). In a range of immortalized and transformed astrocyte derived cell lines and human spinal cord, we show that GFAP-
is naturally part of the endogenous intermediate filaments, although levels were low (
10%). This suggests that GFAP filaments can naturally accommodate a small proportion of assembly-compromised partners. Indeed, two other assembly-compromised GFAP constructs, namely enhanced green fluorescent protein (eGFP)-tagged GFAP and the Alexander disease–causing GFAP mutant, R416W GFAP both showed similar in vitro assembly characteristics to GFAP-
and could also be incorporated into endogenous filament networks in transfected cells, providing expression levels were kept low. Another common feature was the increased association of
B-crystallin with the intermediate filament fraction of transfected cells. These studies suggest that the major physiological role of the assembly-compromised GFAP-
splice variant is as a modulator of the GFAP filament surface, effecting changes in both protein– and filament–filament associations as well as Jnk phosphorylation.
Address correspondence to: Roy A. Quinlan (r.a.quinlan{at}durham.ac.uk)
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