Increased concentration of spectrin is observed in avian dystrophic muscle.

Abstract

A significant increase in the concentration of spectrin has been observed in dystrophic chicken pectoralis major muscle when compared to normal fast-twitch muscle. In normal muscle, a-spectrin-specific immunofluorescence delineates each myofiber with a network pattern of staining at the sarcolemma with little staining within the cytoplasm. In dystrophic fibers, numerous intensely stained areas occur within the cytoplasm and staining at the sarcolemma is increased, thereby obscuring or eliminating the highly regular network arrangement of spectrin usually seen in this region. When immunofluorescence experiments are performed on microsomal vesicles isolated from normal and dystrophic tissues, only a small fraction of normal vesicles are stained, whereas most of the dystrophic vesicles are associated with spectrin. An increase in spectrin concentration is observed using immunoautoradiography of whole muscle and isolated microsomes, thus supporting the immunofluorescent observations described above. The early-age post-hatching when increases in spectrin concentration can be detected and the simplicity of the immunofluorescent technique make this observation useful as a new diagnostic parameter. This observation also shows that the distribution of spectrin and its concentration within nonerythroid cells can be modified by abnormal physiological states; this modification may contribute to subsequent symptoms, such as increased rigidity and abnormal calcium metabolism, that are observed in dystrophy.Shortly after the establishment of a line of chickens with hereditary muscular dystrophy (1, 2), it was observed that the intracellular compartmentalization of Ca2+ in the dystrophic chickens' pectoralis major muscle differed from that observed in normal muscle (3). A decreased affinity for Ca2l has been observed when calcium transport was measured by using erythrocyte membranes of individuals with Duchenne muscular dystrophy (see summary in ref. 4). Of possible relevance to this latter observation are other reports that describe a variety of abnormalities relating to the membraneassociated protein spectrin, or parameters such as membrane deformability, in the erythrocytes of dystrophic chickens and in humans with Duchenne muscular dystrophy (5-12). Spectrin, in erythrocytes, is thought to modulate membrane protein movement, membrane stability, and phospholipid asymmetry by forming a network with other proteins, such as ankyrin, band 4.1, and actin, all of which are closely tethered to the undersurface of the lipid bilayer (see reviews in refs.13-15). Changes in Ca2l levels within erythrocytes can profoundly modify the physical properties of the spectrinmembrane complex (16,17) and since spectrin has been found to be a calmodulin-binding protein (18,19), the implicated relationship between spectrin, calcium metabolism, and membrane properties may be of importance in terms of defining the cellular lesion in dystrophic erythrocytes. However, the applicability of these observations to dystrophic muscle has, until recen...

A Sensitive, Reproducible and Objective Immunofluorescence Analysis Method of Dystrophin in Individual Fibers in Samples from Patients with Duchenne Muscular Dystrophy

“…This was observed throughout all experiments (data not shown) and is in agreement with earlier reports describing qualitative assessments of immunofluorescence images for spectrin in fibers in diseased tissue [12], [13].…”

“…Noteworthy are the mean spectrin intensities measured per fiber, which were typically higher in the DMD and BMD samples compared with the control sample ( Figure S2 ). This was observed throughout all experiments (data not shown) and is in agreement with earlier reports describing qualitative assessments of immunofluorescence images for spectrin in fibers in diseased tissue [12] , [13] .…”

Spectrin-based skeleton as an actor in cell signaling

“…In lymphoid-derived cell lines, spectrin is distributed in the cytoplasm, but appears very often as large aggregates [ 105 ]. These spectrin-rich large aggregates in lymphocytes contain several proteins, such as hsp70, receptor for activated C kinase-1 (RAC-1) and PKCθ (Ca 2+ -independent subfamily of serine/threonine specific protein kinase C) [ 106 , 107 ].…”

Quantitative video microscopy of patch clamped membranes stress, strain, capacitance, and stretch channel activation

“…Pretreatment of the cells (overnight) with 10-5M cytochalasin B did not significantly affect the value of Ka (47 + 7.4 dyn/cm, n = 9), suggesting that the elastic elements are not actin based. The elasticity may be that of the submembrane spectrin network known to exist in these cells (22). The increase in patch area with pressure could arise from three sources: unfolding of unresolved membrane pleats, stretching of a fixed amount of membrane, or the influx of new membrane.…”