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First published online December 15, 2003
doi: 10.1242/10.1242/jcs.00936

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Intermediate filaments are dynamic and motile elements of cellular architecture

Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 E. Chicago Avenue, Chicago, IL 60611, USA

View larger version (54K): [in a new window]   Fig. 1. Neural intermediate filaments move bidirectionally throughout all regions of nerve cells. (A) Differentiated PC12 cells expressing GFP-peripherin show that particles and squiggles, the precursors to long IF, are present in the peripheral regions of cell bodies. (B) These structures can be visualized in the neurites of live cells expressing GFP-peripherin after photobleaching (arrows denote the bleached region). (C) Peripherin particles can also be observed throughout the central and peripheral domains of the growth cones of nontransfected PC12 cells following fixation and staining for peripherin (green) and actin (red). (D) A series of images taken from a live PC12 cell expressing GFP-peripherin. The peripherin particle (see arrows) moved at rates of up to 0.58 µm/s and reversed directions in a region of the cell body during the observation period. Bars, 5 µm (A-C) and 2 µm (D).

View larger version (66K): [in a new window]   Fig. 2. A model for neural intermediate filament transport. Neural IF proteins in the form of nonfilamentous particles, squiggles and longer IF (green) move rapidly along microtubles (blue) in association with kinesin (yellow) and cytoplasmic dynein and dynactin (orange). These motors are responsible for the timely delivery of neural IF particles and squiggles, the precursors to the long IF, to all regions of the neuron including the growth cone (on the right side of cell). Long neural IFs also move along neurites, albeit more slowly than the precursors. Their slower motility might be due to associations with IF-associated proteins such as plectin and bullous pemphigoid antigen (BPAG) (red). In addition, a population of neural IF proteins may move along actin structures (purple) in association with myosin Va (pink) in the cortical and peripheral domains of the growth cone.