| Research Abstract |
One of the striking events during the process of the terminal differentiation in stratified squamous epithelia such as the epidermis is the formation of a 15-nm-thick layer of protein on the inner surface of the cell periphery, termed the cornified cell envelope (CCE). The CCE is now known to be assembled by the accumulation of several distinct proteins, including involucrin, cystatin a (previously known as keratolinin), several small proline-rich proteins (SPRPs), trichohyalin, loricrin, and possibly filaggrin and keratin intermediate filaments. Among these molecules, loricrin is one of the major precursor proteins of CCE.The enzyme transglutaminase 3 (TGase 3) is a member of the transglutaminase family, which includes the coagulation factor XIIIa, the erythrocyte protein band 4.2, transglutaminase 1 and transglutaminase 2. TGase 1 was originally described as membrane-associated keratinocyte transglutaminase but is now known to be widely expressed in epithelial and in some nonepithelial tissues. TGase 1 and TGase 3 are thought to be important enzymes Involved In the formation and assembly of the comified cell envelope of terminally differentiating epidermis. The precursor proteins of the comified cell envelope (CE) are cross-linked by isodipeptide bonds with TGase 1 and 3. Most of the precursor is loricrin and involucrin, but many other proteins such as cystatin a, elafin, small proline-rich proteins and envoplakin seem to be involved. To explore the function of the enzyme transglutaminase 3 (TGase 3), we made a transgenic mouse which expressed truncated TGase 3 protein.
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