KLK7 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Aliases | KLK7 , PRSS6, SCCE, hK7, kallikrein related peptidase 7 | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 604438; MGI: 1346336; HomoloGene: 37998; GeneCards: KLK7; OMA:KLK7 - orthologs | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Kallikrein-related peptidase 7 (KLK7) is a serine protease that in humans is encoded by the KLK7 gene. [5] [6] [7] [8] KLK7 was initially purified from the epidermis and characterised as stratum corneum chymotryptic enzyme (SCCE). [9] It was later identified as the seventh member of the human kallikrein family, which includes fifteen homologous serine proteases located on chromosome 19 (19q13). [10]
Alternative splicing of the KLK7 gene results in two transcript variants encoding the same protein. [8]
KLK7 is secreted as an inactive zymogen in the stratum granulosum layer of the epidermis, requiring proteolytic cleavage of the short N-terminal pro-region to liberate activated enzyme. This may be performed by KLK5 or matriptase, which are in vitro activators of KLK7. [11] [12]
Once active, KLK7 is able to cleave desmocollin and corneodesmosin. [13] These proteins constitute the extracellular component of corneodesmosomes, intercellular cohesive structures which link the intermediate filaments of adjacent cells in the stratum corneum. Proteolysis of corneodesmosomes is required for desquamation, the shedding of corneocytes from the outer layer of the epidermis. This indicates a role for KLK7 in maintaining skin homeostasis. For example, KLK7 expression is highly downregulated at acral surfaces where desquamation is delayed and the epidermis is thick. [14]
Both KLK5 and KLK14, other skin-expressed proteases, also cleave corneodesmosomal proteins. [13] KLK5 is able to undergo autoactivation, as well as activating KLK7 and KLK14, suggesting a KLK skin cascade is responsible for coordinating desquamation. [12]
KLK7 activity is regulated by a number of endogenous protein inhibitors including LEKTI, [15] [16] SPINK6, [17] elafin [18] and alpha-2-Macroglobulin-like 1. [19] Both Zn2+ and Cu2+ ions are also able to inhibit KLK7. [18]
KLK7 is a chymotrypsin-like serine protease, preferring to cleave proteins at the residues tyrosine, phenylalanine or leucine. [20] Analysis of peptide substrate hydrolysis indicates a strong preference for tyrosine at P1. [21]
Dysregulation of KLK7 has been linked to several skin disorders including atopic dermatitis, [22] [23] psoriasis [24] and Netherton syndrome. [25] [26] These diseases are characterised by excessively dry, scaly and inflamed skin, due to a disruption of skin homeostasis and correct barrier function.
Overexpression of KLK7 may provide a route for metastasis in ovarian, [27] breast, [28] pancreatic, [29] cervix, [30] and melanoma [31] cancers by excessive cleavage of cell junction proteins. It may also be underexpressed in lung cancer. [32]
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss.
The stratum corneum is the outermost layer of the epidermis. Consisting of dead tissue, it protects underlying tissue from infection, dehydration, chemicals and mechanical stress. It is composed of 15–20 layers of flattened cells with no nuclei and cell organelles.
Desquamation, or peeling skin, is the shedding of dead cells from the outermost layer of skin.
The stratum granulosum is a thin layer of cells in the epidermis lying above the stratum spinosum and below the stratum corneum. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer. These cells contain keratohyalin granules, which are filled with histidine- and cysteine-rich proteins that appear to bind the keratin filaments together. Therefore, the main function of keratohyalin granules is to bind intermediate keratin filaments together.
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known paralogue, while tissue kallikrein-related peptidases (KLKs) encode a family of fifteen closely related serine proteases. These genes are localised to chromosome 19q13, forming the largest contiguous cluster of proteases within the human genome. Kallikreins are responsible for the coordination of various physiological functions including blood pressure, semen liquefaction and skin desquamation.
In cell biology, lamellar bodies are secretory organelles found in type II alveolar cells in the lungs, and in keratinocytes in the skin. They are oblong structures, appearing about 300-400 nm in width and 100-150 nm in length in transmission electron microscopy images. Lamellar bodies in the alveoli of the lungs fuse with the cell membrane and release pulmonary surfactant into the extracellular space.
Netherton syndrome is a severe, autosomal recessive form of ichthyosis associated with mutations in the SPINK5 gene. It is named after Earl W. Netherton (1910–1985), an American dermatologist who discovered it in 1958.
Corneocytes are terminally differentiated keratinocytes and compose most of the stratum corneum, the outermost layer of the epidermis. They are regularly replaced through desquamation and renewal from lower epidermal layers and are essential for its function as a skin barrier.
Kallikrein-6 is a protein that in humans is encoded by the KLK6 gene. Kallikrein-6 is also referred to as neurosin, protease M, hK6, or zyme. It is a 223 amino acid sequence, derived from its 244 original form, which contains a 16 residue presignal and 5 residue activation peptide.
Kallikrein-10 is a protein that in humans is encoded by the KLK10 gene.
Kallikrein-5, formerly known as stratum corneum tryptic enzyme (SCTE), is a serine protease expressed in the epidermis. In humans it is encoded by the KLK5 gene. This gene is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19. Its expression is up-regulated by estrogens and progestins. Alternative splicing results in multiple transcript variants encoding the same protein.
Lympho-epithelial Kazal-type-related inhibitor (LEKTI) also known as serine protease inhibitor Kazal-type 5 (SPINK5) is a protein that in humans is encoded by the SPINK5 gene.
Corneodesmosin is a protein that in humans is encoded by the CDSN gene.
Kallikrein-8 is a protein that in humans is encoded by the KLK8 gene.
Kallikrein-14 is a protein that in humans is encoded by the KLK14 gene.
Kallikrein-12 is a protein that in humans is encoded by the KLK12 gene.
Trichorrhexis invaginata is a distinctive hair shaft abnormality that may occur sporadically, either in normal hair or with other hair shaft abnormalities, or regularly as a marker for Netherton syndrome. The primary defect appears to be abnormal keratinization of the hair shaft in the keratogenous zone, allowing for intussusception of the fully keratinized and hard distal shaft into the incompletely keratinized and soft proximal portion of the shaft.
Term ''kallikrein 7 may refer to:
Lympho-epithelial Kazal-type related inhibitor 2 (LEKTI-2) is a protein encoded by the SPINK9 gene in humans. SPINK9 is a member of a gene family cluster located on chromosome 5q33.1, which includes SPINK5 and SPINK6. LEKTI-2 is an inhibitor of KLK5.
Stratum corneum chymotryptic enzyme is an enzyme. This enzyme catalyses the following chemical reaction