Mutations signaling molecules

Agammaglobulinemia or hypogammaglobulinemia Mutations in genes that code for immunoglobulin light or heavy chains or their associated signaling molecules. 

The chloride channel is vital for proper absorption of salt (NaCl) and water across the plasma membranes of the epithelial cells that line ducts and tubes in tissues such as lungs, liver, small intestine, and sweat glands. Chloride transport occurs when signal molecules open CFTR Cl channels in the apical (top) membrane surface of epithelial cells. In CF the failure of CFTR channels results in the retention of Cl within the cells. A thick mucus or other secretion forms because osmotic pressure causes the excessive uptake of water. The most obvious features of CF are lung disease (obstructed air flow and chronic bacterial infections), and pancreatic insufficiency (impaired production of digestive enzymes that can result in severe nutritional deficits). In the majority of CF patients, CFTR is defective because of a deletion mutation at Phe508, which causes... 

Growth factor receptor tyrosine kinases can activate multiple pathways that lead to mitogenesis. There are many examples of growth factor receptor overexpression in tumor cells, and their constitutive activation by various mechanisms is related to tumor formation or progression (Karunagaran et al., 1996 Tsujimura, 1996 Empereur et al., 1997 Borset et al., 1996 Moscatello et al., 1996 Schmidt et al., 1997 Santoro et al., 1995). Many of the above-described MSP-Ron signaling molecules are known to cause cell transformation. For example, Ras genes are mutated in 20-30% of human cancers and the encoded proteins are believed to contribute to the patho-... 

Dystroglycan, an adhesion receptor expressed by muscle cells, forms a large complex with dystrophin, other adapter proteins, and signaling molecules (see Figure 6-29). This complex links the actln cytoskeleton to the surrounding matrix, providing mechanical stability to muscle. Mutations in various components of this complex cause different types of muscular dystrophy. 

The RAS protein is activated in response to ligand-induced receptor aggregation at the inner surface of the plasma membrane where complexes of signaling molecules accumulate to attain a critical level for signal transduction (Figure 2). Activating mutations in RAS, of the type found in human tumors, bypass the need for... 

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