Alpha-6 / Beta-4 integrin
The alpha-6/beta-4 integrin is expressed on different cell-types. They are expressed on immature thymocytes, on squamous epithedlia, on subsets of endothelial cells, on Schwann cells and also on fibroblasts in the peripheral nervous system. In stratified epithelia like the skin, alpha-6/beta-4 is concentrated in dense structures which are called hemidesmosomes. These dense structures are involved in the attachment of basal cells to the underlying basement membranes. This is achieved by connection of the intermediate filaments to the extracellular matrix via this integrin. All the other integrins use actin filaments for this purpose in stead of intermediate filaments. The ligands for the alpha-6/beta-4 integrin are laminin-1 and laminin-5. The afffinity for laminin-5 however is much stronger. In hemidesmosomes it is found attached to laminin-5. The different alpha-6 splice variants do not influence the ligand specificities of the integrin.
From studies with knockout mice it was found that in the absense of the integrin (beta-4 knockout or alpha-6 knockout) no hemidesmosomes were present, suggesting that the integrin is neccesary for the formation or initiation of hemidesmosomes. these mice showed severe blistering of the skin and died soon after birth.
Last updated on 24/02/97
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