Journal of Cell Science, Vol 113, Issue 11 2023-2034, Copyright © 2000 by Company of Biologists

JOURNAL ARTICLES

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

NV Hayes, C Scott, E Heerkens, V Ohanian, AM Maggs, JC Pinder, E Kordeli and AJ Baines
Department of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, England.

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.

This article has been cited by other articles:

				P. A. Bignone, M. D. A. King, J. C. Pinder, and A. J. Baines Phosphorylation of a Threonine Unique to the Short C-terminal Isoform of betaII-Spectrin Links Regulation of {alpha}-beta Spectrin Interaction to Neuritogenesis J. Biol. Chem., January 12, 2007; 282(2): 888 - 896. [Abstract] [Full Text] [PDF]

				P. M. Bennett, A. M. Maggs, A. J. Baines, and J. C. Pinder The Transitional Junction: A New Functional Subcellular Domain at the Intercalated Disc Mol. Biol. Cell, April 1, 2006; 17(4): 2091 - 2100. [Abstract] [Full Text] [PDF]

				P. J. Mohler, W. Yoon, and V. Bennett Ankyrin-B Targets {beta}2-Spectrin to an Intracellular Compartment in Neonatal Cardiomyocytes J. Biol. Chem., September 17, 2004; 279(38): 40185 - 40193. [Abstract] [Full Text] [PDF]

				S. Park, M. S. Caffrey, M. E. Johnson, and L. W.-M. Fung Solution Structural Studies on Human Erythrocyte {alpha}-Spectrin Tetramerization Site J. Biol. Chem., June 6, 2003; 278(24): 21837 - 21844. [Abstract] [Full Text] [PDF]

				V. Bennett and A. J. Baines Spectrin and Ankyrin-Based Pathways: Metazoan Inventions for Integrating Cells Into Tissues Physiol Rev, July 1, 2001; 81(3): 1353 - 1392. [Abstract] [Full Text] [PDF]

				S. Berghs, D. Aggujaro, R. Dirkx , Jr., E. Maksimova, P. Stabach, J.-M. Hermel, J.-P. Zhang, W. Philbrick, V. Slepnev, T. Ort, et al. {beta}IV Spectrin, a New Spectrin Localized at Axon Initial Segments and Nodes of Ranvier in the Central and Peripheral Nervous System J. Cell Biol., November 20, 2000; 151(5): 985 - 1002. [Abstract] [Full Text] [PDF]