title: Not just a plasma membrane protein: in cardiac muscle cells alpha-II spectrin also shows a close association with myofibrils.
abstract: Spectrin and its associated proteins are essential for the integrity of muscle cells and there is increasing evidence for their involvement in signalling pathways as well as having a structural function in mediating stress. Spectrin is a multigene family and it is essential to determine which isoforms are present and their location in the cell. In heart muscle, we have found that one spectrin isoform, alphaII-spectrin, is strongly represented and, using immunofluorescence, we show that it lies within the contractile fibres near the Z-disc as well as on the cardiomyocyte plasma membrane. Electron microscopy of immunogold-labelled cryosections reveals statistically significant clustering of gold particles near the Z-disc, within and close to the edge of myofibrils. betaII-spectrin and ankyrin-R and G are both known to occupy this region. We suggest that alphaIIbetaII spectrin tetramers with ankyrin organise and/or stabilise cardiac muscle cell membrane components relative to the contractile apparatus.
authors.affiliation: The Randall Centre for Molecular Mechanisms of Cell Function, New Hunt's House, King's College London, Guy's Campus, London SE1 1UL, UK. pauline.bennett@kcl.ac.uk
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Bennett
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Baines
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Lecomte
authors.forename: Alison M
authors.initials: AM
authors.lastname: Maggs
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Pinder
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry; D016009:Chi-Square Distribution; D064211:Connectin; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D009124:Muscle Proteins / Q000032:analysis; D009206:Myocardium / Q000737:chemistry / Q000166:cytology; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D009210:Myofibrils / Q000737:chemistry / Q000502:physiology*; D010210:Papillary Muscles / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure; D020033:Protein Isoforms / Q000032:analysis / Q000502:physiology; D011494:Protein Kinases / Q000032:analysis; D013049:Spectrin / Q000032:analysis / Q000502:physiology*
chemical_list: D064211:Connectin; D009124:Muscle Proteins; D020033:Protein Isoforms; D013049:Spectrin; D011494:Protein Kinases