Identification of a novel C-terminal variant of beta II spectrin: two isoforms of beta II spectrin have distinct intracellular locations and activities.

Hayes, N.V.L. and Scott, C. and Heerkens, E. and Ohanian, V. and Maggs, A.M. and Pinder, J.C. and Kordeli, E. and Baines, A.J. (2000) Identification of a novel C-terminal variant of beta II spectrin: two isoforms of beta II spectrin have distinct intracellular locations and activities. Journal of cell science, 113 (11). pp. 2023-34. ISSN 0021-9533. (The full text of this publication is not available from this repository)

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Abstract

It is established that variations in the structure and activities of betaI spectrin are mediated by differential mRNA splicing. The two betaI spectrin splice forms so far identified have either long or short C-terminal regions. Are analogous mechanisms likely to mediate regulation of betaII spectrins? Thus far, only a long form of betaII spectrin is reported in the literature. Five human expressed sequence tags indicated the existence of a short splice variant of betaII spectrin. The occurrence and DNA sequence of the short C-terminal variant was confirmed by analysis of human and rat cDNA. The novel variant lacks a pleckstrin homology domain, and has 28 C-terminal residues not present in the previously recognized longer form. Transcripts of the short C-terminal variant (7.5 and 7. 0 kb) were most abundant in tissues originating from muscle and nervous system. Antibodies raised to a unique sequence of short C-terminal variant recognized 240 kDa polypeptides in cardiac and skeletal muscle and in nervous tissue; in cerebellum and forebrain, additional 270 kDa polypeptides were detected. In rat heart and skeletal muscle, both long and short C-terminal forms of betaII spectrin localized in the region of the Z line. The central region of the sarcomere, coincident with the M line, was selectively labeled with antibodies to the short C-terminal form. In cerebellum, the short form was not detectable in parallel fibers, structures in which the long form was readily detected. In cultured cerebellar granule neurons, the long form was dominant in neurites, with the short form being most abundant in cell bodies. In vitro, the short form was found to lack the binding activity for the axonal protein fodaxin, which characterizes the C-terminal region of the long form. Subcellular fractionation of brain revealed that the short form was scarcely detectable in post-synaptic density preparations, in which the long form was readily detected. We conclude that variation in the structure of the C-terminal regions of betaII spectrin isoforms correlates with their differential intracellular targeting.

Item Type: Article
Uncontrolled keywords: spectrin; muscle; heart; neuron
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Cell & Developmental Biology Group
Depositing User: Anthony Baines
Date Deposited: 21 May 2009 08:50
Last Modified: 15 Jun 2012 09:31
Resource URI: http://kar.kent.ac.uk/id/eprint/8644 (The current URI for this page, for reference purposes)
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