Basal lamina collagen type

Basal laminas are specialized areas of the ECM that surround epithelial and some other cells (eg, muscle cells) here we discuss only the laminas found in the renal glomerulus. In that strucmre, the basal lamina is contributed by two separate sheets of cells (one endothelial and one epithelial), each disposed on opposite sides of the lamina these three layers make up the glomerular membrane. The primary components of the basal lamina are three proteins—laminin, entactin, and type IV collagen—and the GAG heparin or heparan sulfate. These components are synthesized by the underlying cells. 

Fig. 3.2 Relationship of the connective tissue stroma to an epithelium. Fibroblasts secrete unique types of laminin proteins that interact with each other and type IV collagen, to form a basal lamina (yellow) that is tightly attached to the connective tissue (stromal) cells and also to the associated muscle or epithelial cell. The kidney glomerulus is a specialized tissue in which the stroma is absent and endothelial cells and epithelial cells are separated by the basal lamina which filters the blood as the first step in urine collection. The attachment of an epithelium to stromal collagen is discussed in detail in Chap. 5 (Fig. 19-55 in The Molecular Biology of the Cell. B. Alberts et al., 4th Ed. 2002. Garland Science, Taylor Francis Group, NY)...

The kidney contains small amounts of fibrillar collagen, but its major collagen is a non-fibrillar network collagen (type IV), a part of basal laminas called the lamina densa (Sect. 5.1.1). Basal laminas are especially well developed in the kidney as exemplified in the glomerulus (Fig. 3.2). The collagen contents of various tissues are indicated in Table 3.2 and their fiber arrangements in Table 3.3. 

Type VII collagen is a non-fibrous, anchoring fibril that binds large type I collagen fibers in the stroma to the lamina densa section of the basal lamina. Type VII procollagen... 

Plakin proteins link intracellular keratin intermediate filaments to hemidesmosomes of basal epidermal cells, or to desmosomes on suprabasal epidermal cells (Sect. 5.2.1), whereas type XVII collagen (the only collagen secreted by epithelial cells ) and integrins attach hemidesmosomes to a basal lamina. Three p 1 integrins (with al, a3 or a5 partners)... 

FIGURE 6-13 Major components of the basal lamina. Schematic model of basal lamina showing the organization of the major protein components. Type IV collagen and laminin each form two-dimensional networks, which are cross-linked by entactin and perlecan molecules. [Adapted from B. Alberts et al., 1994, Molecular Biology of the Cell, 3d ed., Garland, p. 991.1... 

Sheet-Forming Type IV Collagen Is a Major Structural Component in Basal Laminae... 

Four ECM proteins are found in all basal laminae (see Figure 6-13) type IV collagen, laminin (a multiadhesive matrix protein), entactin (nidogen), and perlecan (a proteoglycan). 

Many of the extracellular materials are filaments made from fibrous proteins, mainly collagen and elastin, and adhesion proteins such as fibronectin and laminin. Collagens form a family of proteins with a tissue-specific distribution, including types inifound in connective tissue such as filamentsand types IV and Vfound in basal laminae forming sheets of tissue. 

---