Spatial Sorting of Tropomyosin Isoforms
Numerous reports detail that tropomyosin isoforms are sorted to different intracellular locations, often associating with actin filament populations that are involved in specific processes. Direct visualization of spatial segregation of isoforms was initially observed by Burgoyne and Norman and soon after by Lin and co-workers. They observed that specific isoforms were associated with distinct cellular structures. Using specific antibodies they were able to identify the presence of both HMW and the LMW isoforms of the γ-gene in stress fibers, however only LMW isoforms were detected in ruffling membranes.
These studies have been extended to a number of cell types with similar results. Extensive studies in neuronal cells, fibroblasts, skeletal muscle and osteoclast cells, has further highlighted the complex association tropomyosin isoforms have with cellular structures. These studies have led to the realization that the regulation of isoform sorting is extremely complex and highly regulated.
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