Involucrin is a protein component of human skin and in humans is encoded by the IVLgene.[3][4] In binding the protein loricrin, involucrin contributes to the formation of a cell envelope that protects corneocytes in the skin.
This gene is mapped to 1q21, among calpactin I light chain, trichohyalin, , loricrin, and .[4]
Function[]
Involucrin is a highly reactive, soluble, transglutaminasesubstrateprotein present in keratinocytes of epidermis and other stratified squamous epithelia.[5][6] It first appears in the cellcytosol, but ultimately becomes cross-linked to membrane proteins by transglutaminase thus helping in the formation of an insoluble envelope beneath the plasma membrane functioning as a glutamyl donor during assembly of the cornified envelope.[7]
Involucrin is synthesised in the stratum spinosum and cross linked in the stratum granulosum by the transglutaminase enzyme that makes it highly stable. Thus it provides structural support to the cell, thereby allowing the cell to resist invasion by micro-organisms.[citation needed]
Apigenin, a plant-derived flavanoid that has significant promise as a skin cancerchemopreventive agent, has been found to regulate normal human keratinocyte differentiation by suppressing involucrin, and this is associated with reduced cell proliferation without apoptosis.[8]
Clinical significance[]
As one of the precursor proteins of the cornified cell envelope, involucrin is markedly increased in inflammatory skin diseases such as psoriasis[9]
Lamellar ichthyosis involves a decrease in expression of involucrin. This decrease could contribute to the altered desquamation process seen in the disease, since the clinical improvement associated with retinoid treatment is accompanied by increased expression of involucrin.[10]
Structure[]
Involucrin consists of a conservedN-terminal region of about 75 amino acid residues followed by two extremely variable length segments that contain glutamine-rich tandem repeats. The glutamine residues in the tandem repeats are the substrate for the transglutaminase in the cross-linking reaction. The total size of the protein varies from 285 residues (in dog) to 835 residues (in orangutan).[citation needed]
^Takahashi H, Hashimoto Y, Ishida-Yamamoto A, Iizuka H (September 2005). "Roxithromycin suppresses involucrin expression by modulation of activator protein-1 and nuclear factor-kappaB activities of keratinocytes". Journal of Dermatological Science. 39 (3): 175–82. doi:10.1016/j.jdermsci.2005.03.006. PMID16140218.
Rice RH, Green H (November 1979). "Presence in human epidermal cells of a soluble protein precursor of the cross-linked envelope: activation of the cross-linking by calcium ions". Cell. 18 (3): 681–94. doi:10.1016/0092-8674(79)90123-5. PMID42494. S2CID23066704.
Volz A, Korge BP, Compton JG, Ziegler A, Steinert PM, Mischke D (October 1993). "Physical mapping of a functional cluster of epidermal differentiation genes on chromosome 1q21". Genomics. 18 (1): 92–9. doi:10.1006/geno.1993.1430. PMID8276421.
Ng DC, Su MJ, Kim R, Bikle DD (January 1996). "Regulation of involucrin gene expression by calcium in normal human keratinocytes". Frontiers in Bioscience. 1: a16-24. doi:10.2741/A101. PMID9159190.