Seven Kinds of Intermediate Filament Networks in the Cytoplasm of Polarized Cells: Structure and Function

Abstract

Intermediate filaments (IFs) are involved in many important physiological functions, such as the distribution of organelles, signal transduction, cell polarity and gene regulation. However, little information exists on the structure of the IF networks performing these functions. We have clarified the existence of seven kinds of IF networks in the cytoplasm of diverse polarized cells: an apex network just under the terminal web, a peripheral network lying just beneath the cell membrane, a granule-associated network surrounding a mass of secretory granules, a Golgi-associated network surrounding the Golgi apparatus, a radial network locating from the perinuclear region to the specific area of the cell membrane, a juxtanuclear network surrounding the nucleus, and an entire cytoplasmic network. In this review, we describe these seven kinds of IF networks and discuss their biological roles.

Semi-Nested Real-Time Reverse Transcription Polymerase Chain Reaction Methods for the Successful Quantitation of Cytokeratin mRNA Expression Levels for the Subtyping of Non-Small-Cell Lung Carcinoma Using Paraffin-Embedded and Microdissected Lung Biopsy Specimens

“…CK18 is a low molecular weight keratin and is largely expressed in all simple epithelia, ductal epithelia, pseudostratified epithelia, and carcinoma cells arising from simple epithelia, except for basal cell carcinoma and squamous cell carcinoma [5]. Furthermore, CK18 is localized in apical areas of the rabbit duodenum and columnar cells, and the involvement of CK18 in the apex and peripheral networks have been suggested [11]. CK18 has been reported to function in intercellular signaling as a growth factor in conjunction with CK8 [38] and has been used as a serum biomarker for carcinoma.…”

“…In humans, 54 functional keratin genes exist and are expressed in specific patterns related to the epithelial type and the cellular differentiation. These proteins have been suggested to play a functional role via cell-cell contacts [11, 37]. In tumor diagnosis, in particular, the immunohistochemical expressions of CK5, CK7, CK8/18, CK19, and CK20 have great importance in the precise classification, subtyping, and detection of unclear metastasis [5].…”

A novel function for the MAP kinase SMA-5 in intestinal tube stability

“…These layers are anchored to the apical junctional complex in vertebrates including fish (Markl and Franke, 1988), amphibians (Maurizii et al. , 2000), and mammals (Iwatsuki and Suda, 2010). This remarkable distribution is also conserved in the nematode Caenorhabditis elegans , in which intermediate filaments localize to the prominent endotube (Bossinger et al.…”

The novel intestinal filament organizer IFO-1 contributes to epithelial integrity in concert with ERM-1 and DLG-1

“…Depending on the cell type and cell cycle stage IFs are very differently arranged. They form intricate three dimensional networks in cultured cells, thick bundles in keratinocytes and neurons, granules in mitotic cells or dense fibrous sheets below the apical terminal web of intestinal cells (Iwatsuki and Suda, 2010). How these different types of spatial arrangement are established and maintained is not very well understood.…”