Interactions of intermediate filaments with cell structures

Intermediate filaments (IF) are unique components of the cytoskeleton of most eukaryotic cells. Also the nuclear lamins are now recognized to be IF-like proteins, providing the nucleus with a putative skeleton for chromatin attachment. Immunofluorescence and whole-mount electron microscopic studies reveal that IF form a cytoplasmic network that surrounds the nucleus and extends to cell surface, as ‘mechanical integrators of cellular space’. It seems however unlikely that IF in the cell accomplish a merely structural role, considering the diversity of IF proteins and the complex regulation of their gene expression. In this work we primarily present electron microscopic data that points to the presence of interactions between IF and several cellular components, namely the nucleus, plasma membrane, other cytoskeletal elements, cytoplasmic organelles and ribonucleoproteins. Although the functional significance of such interactions remains to be demonstrated, assumptions like involvement of IF in information transfer or cytoskeleton-dependent control of gene expression represent attractive hypothesis for future research.