Intermediate filament functions: dismissed & revealed |
In the early 1980's,
when I started working on IFs, they were arguably the most enigmatic
component of the cytoskeleton. While
microtubules and microfilaments are ubiquitous and essential components
of eukaryotic cells, IFs
were clearly not. |
In fact there is an evolutionary oddity, insects (such a Drosophila melanogaster) appear not to have cytoplasmic IFs, although they do have lamins. Nevertheless, IFs are a major component of the cytoskeleton in many cell types and a nuclear lamina appears to be present in most eukaryotes. Confocal image of the keratin-type IF network (red filaments) of a cultured epithelial cell. The cell also expressed a nuclealy-localized green fluorescent protein chimera (plakophilin-1-GFP). The typical approach to studying the function of a structure is to disrupt it, and then watch the effects on the cell. |
A major obstacle to understanding IFs was the absence of reagents that specifically disrupted IF organization. |
Antibody injection can be used to disrupt IF organization in a wide range of cells. Working initially at Cold Spring Harbor, and later in London, E. Birgitte Lane generated a number of monoclonal antibodies directed against the keratin-type IF proteins of simple epithelial cells. Different monoclonal antibodies had different effects on keratin filament organization. |
IFs had been postulated to play a major roll in the establishment and maintanence of cellular morphology. We used antibody injection to test these ideas. Injection of the monoclonal antikeratin antibody LE61 into cultured epithelial cells induces the disruption of the keratin-type IF network. |
One can disrupt keratin organization in one cell and examine desmosome integrity and keratin organization in neighboring cells. The surprising result was that there was no apparent change in cellular morphology, movement or intracellular organization. |
In
particular our long-time collaborator Bob
Evans carried out
an elegant and extensive analysis of variants of the human cell line
SW13 that lacked all detectable cytoplasmic IFs, and found no apparent
difference compared to sister lines that contained IFs. |
1953-2004
Michael Klymkowsky and associates last updated:24 October 2004 |