Cell junctions

Fyn is a nonreceptor tyrosine kinase related to Src that is frequently found in cell junctions. Die protein is N-myristoylated and palmitoylated and thereby becomes associated with caveolae-like membrane microdomains. Fyn can interact with a variety of other signaling molecules and control a diversity of biological processes such as T cell receptor signaling, regulation of brain function, and adhesion mediated signaling. 

Fig. 5.12 (a) Synaptic types along dendritic spines of M/T and GC units uni-, and bi-directional junctions, (b) Transmitter systems at a reciprocal synapse, Mitral-Granule cell junction. [Glu, glutamate (R, receptor) GABA, y-aminobutyric acid (R, receptor) E, intracellular effector and aAR, alpha-adrenergic receptor.]. (From Hayashi et al., 1993.)... 

Interruptions (20-80 nm) between cell junctions membrane thickness 4-6 nm basement membrane continuous... 

Yamashita et al. [82] added up to 10 mM taurocholic acid, cholic acid (cmc 2.5 mM), or sodium laurel sulfate (SLS low ionic strength cmc 8.2 mM) to the donating solutions in Caco-2 assays. The two bile acids did not interfere in the transport of dexamethasone. However, SLS caused the Caco-2 cell junctions to become leakier, even at the sub-CMC 1 mM level. Also, the permeability of dexamethasone decreased at 10 mM SLS. 

Skeletal and cardiac muscles also have important differences. Skeletal muscle cells are elongated and run the length of the entire muscle furthermore, these cells have no electrical communication between them. Cardiac muscle cells, on the other hand, branch and interconnect with each other. Intercellular junctions found where adjoining cells meet end-to-end are referred to as intercalated discs. Two types of cell-to-cell junctions exist within these discs. Desmosomes hold the muscle cells together and provide the structural support needed when the heart beats and exerts a mechanical... 

Yet another family of junction adhesion molecules (JAMs) was recently located at the tight junctions of both endothelial and epithelial cells. The intracellular domain of JAM-1 also interacts with structural and signaling proteins, such as ZO-1 and cingulin. Lastly, the molecular organization of the endothelial cell junctions includes two other cell-cell contact Ca2+-dependent cadherin-catenin systems. These make up the adherens junction common to all endothelial cell junctions. 

Mechanical functions of cells require interactions between integral membrane proteins and the cyto-skeleton. These functions include organization of signaling cascades, formation of cell junctions and regulation of cell shape, motility, endo- and exocytosis. Several different families of membrane-associated proteins mediate specific interactions among integral membrane proteins, cytoskeletal proteins and contractile proteins. Many of these linker proteins consist largely of various combinations of conserved protein-association domains, which often occur in multiple variant copies. 

To visualize whether or not wood can be delignified by laccase III, ultraviolet photomicrographs (280nm) were taken before and after treatment of 0.5 mjLt cross-sections of red pine with laccase III (Figure 11). After enzyme treatment areas having an absorbance less than 0.2 in the secondary wall, and an absorbance less than 0.4 in the middle lamella, appeared. Each part of the secondary wall, middle lamella, and cell junction was subjected to ultraviolet microscopy, and absorption curves in the 240-300nm region were determined. The absorption curves of three samples after treatment... 

The existence of a barrier between the blood and testes is indicated by the absence of staining in testicular tissue after the intravascular injection of dyes. Morphological studies indicate that the barrier lies beyond the capillary endothelial cells and is most likely to be found at the specialized Sertoli-Sertoli cell junction. It appears that Pgp, the efflux transporter protein, also plays a role in forming this blood-testis barrier. This protein probably plays a role in preventing certain chemotherapeutic agents from reaching specific areas of the testis and thus hinders treatment of the neoplasm. 

Azarnia R, Dahl G, Loewenstein WR Cell junction and cyclic AMP. III. Promotion of junctional membrane permeability and junctional membrane particles in a junction-deficient cell type. J Membr... 

Loewenstein WR, Kanno Y, Socolar SJ Quantum jumps of conductance during formation of conductance channels at cell-cell junction. Nature 1978 274 133-136. 

Rose B, Loewenstein WR Permeability of cell junctions depends on local cytoplasmic calcium activity. Nature 1975 254 250-252. 

Schwarzmann G, Weigandt H, Rose B, Zimmermann A, Ben Haim D, Loewenstein WR Diameter of the cell-to-cell junctional membrane channels as probed with neutral molecules. Science 1981 213 551— 553. 

Electron crystallography 131 Electron micrograph of bacteria 4 of cell junctions 27 of plant cell 13 of starch granules 172 of viruses 246... 

Spray, D.C. (1994) Physiological and pharmacological regulation of gap junction channels. Molecular Mechanisms of Epithelial Cell Junctions From Development to Disease. Editors. Chi 195-215. RG Landes, Austin... 

The outer surface of the cornea is covered with a smooth layer of stratified corneal epithelium (Figure 3.4). The lower layer of cells is columnar in shape and rests on a basement membrane that sits on top of a thick limiting structure termed Bowman s membrane derived from the corneal stroma below. The corneal stroma is composed of parallel bundles of collagen fibrils termed lamellae and rows or layers of branching corneal fibroblasts termed keratocytes. The posterior of the cornea is covered with a low cuboidal epithelium with a wide basement membrane (Descemet s membrane) and rests on the posterior portion of the corneal stroma. The corneal epithelium is normally under tension due to the pressure that is present in the anterior chamber just behind the cornea. The intraocular pressure is between 10 and 20 mm of mercury and is enough to cause the cornea to contract about 5% when it is excised from the eye. Therefore this pressure must be transferred between epithelium via cell-cell junctions. 

Thus, external forces applied to the epidermis and/or internal forces present in dermis are transmitted through the cornified layer and lead to stretching of keratinocyte-keratinocyte cell junctions and the epidermal-dermal junction. These forces appear to be transmitted between epithelial cells via cadherins and may result in activation of secondary messengers which alter gene expression and protein synthesis. 

---