| PLEKHA7 | |||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | PLEKHA7 , pleckstrin homology domain containing A7 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 612686 MGI: 2445094 HomoloGene: 52172 GeneCards: PLEKHA7 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
| Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||
PLEKHA7 (Pleckstrin homology domain-containing family A member 7) is an adherens junction (AJ) protein, involved in the junction's integrity and stability.
The protein was discovered in Masatoshi Takeichi’s lab while looking for potential binding partners for the N-terminal region of p120. PLEKHA7 was identified by mass spectrometry in lysates of human intestinal carcinoma (Caco-2) cells in a GST-pull down using N-terminal GST-fusion p120 catenin as bait. [5] It was also independently discovered in Sandra Citi’s group as a protein interacting with globular head domain of the Paracingulin in a yeast two-hybrid screen. PLEKHA7 localizes at epithelial zonular AJs. [6]
The structure of PLEKHA7 is characterized by two WW domains followed by a Pleckstrin homology domain (PH) in the N-terminal region. In the C-terminal half, the protein contains three coiled coil (CC) domains and two Proline-rich (Pro) domains. [6] PLEKHA7 has been detected in different isoforms in a tissue specific manner. Two isoforms of 135 kDa and 145 kDa have been reported in colon, liver, lung, eye, pancreas, kidney and heart. Additionally, two major transcripts of 5.5 kb and 6.5 kb have been identified in brain, kidney, liver, small intestine, placenta and lung, while only one PLEKHA7 mRNA transcript of 5.5 kb is identified in heart, brain, colon and skeletal muscle. [6]
In vitro interaction studies were pursued to map the interaction(s) of PLEKHA7 with p120 (residues 538-696), Nezha (CAMSAP3) (residues 680-821), paracingulin (residues 620-769) and Afadin (residues 120-374). [7] The protein PDZD11 was identified as a protein interacting through its N-terminal region with the N-terminal WW domain of PLEKHA7, based on 2-hybrid screen and analysis of PLEKHA7 immunoprecipitates [8] Unlike most other AJ proteins, but similar to afadin, PLEKHA7 is exclusively detected in the zonular apical part of AJ, but not in the “puncta adherentia” along lateral membranes of the epithelial cells. [6] Cellular localization and tissue distribution of PLEKHA7 has been confirmed by Immunoelectron microscopy (Immuno-EM) of wild type and knock down intestinal epithelial tissues. [6]
The first identified function of PLEKHA7 was is to contribute to integrity and stability of the zonula adherens junctions by linking the E-cadherin/p120 complex to the minus ends of microtubules (MTs) through Nezha (CAMSAP3). [5] The PLEKHA7-Nezha- MTs complex allows transport of the KIFC3 (a minus end directed motor) to the AJ. However, in Eph4 cell line, PLEKHA7 is recruited to E-cadherin based AJ by Afadin, independently of p120. [7] PLEKHA7 knockdown studies in Madin-Darby canine kidney (MDCK) cells indicated its requirement for the AJ localization of paracingulin. [9] Furthermore, the PLEKHA7 homolog in zebrafish, Hadp1, is required for proper heart function and morphogenesis in embryo, regulating the intracellular Ca2+
dynamics through the phosphatidylinositol 4-kinase (PIK4) pathway. [10]
In 2015, researchers discovered that PLEKHA7 recruits the so-called microprocessor complex (association of Drosha and DGCR8 proteins) to a growth-inhibiting site (apical zonula adherens) in epithelial cells instead of sites at basolateral areas of cell–cell contact containing tyrosine-phosphorylated p120 and active Src. Loss of PLEKHA7 disrupts miRNAs regulation, causing tumorigenic signaling and growth. Restoring normal miRNA levels in tumor cells can reverse that aberrant signaling. [11] [12] [13] In 2015 it was also discovered that PLEKHA7 has a role in controlling susceptibility to Staphylococcus aureus alpha-toxin [14] Cells lacking PLEKHA7 are injured by the toxin, but recover after intoxication. Mice knockout for PLEKHA7 are viable and fertile, and when infected with methycillin-resistant S. aureus USA300 LAC strain they show a decreased disease severity in both skin infection and lethal pneumonia, thus identifying PLEKHA7 as a potential nonessential host target to reduce S. aureus virulence during epithelial infections. [14]
In 2016, researchers found that PLEKHA7 recruits the small PDZ protein PDZD11 to adherens junctions, thus resulting in the stabilisation of nectins at adherens junctions. [15] Knock-out of PLEKHA7 results in the loss of PDZD11 from epithelial adherens junctions, and this is rescued by the introduction of exogenous PLEKHA7. [15] The N-terminal 44 residues of PDZD11 interact with the first WW domain of PLEKHA7. [15] In the absence of either PLEKHA7 or PDZD11, the amount of nectin-3 and nectin-4 detected at junctions is decreased, as well as total nectin levels, through proteasome-mediated degradation. [15] PDZD11 interacts directly with the cytoplasmic PDZ-binding motif of nectins, through its own PDZ domain. [15] Proximity ligation assay shows that PLEKHA7 is associated to nectins in a PDZD11-dependent manner. [15] Nectins are the second major class of transmembrane adhesion molecules at adherens junctions, besides cadherins. Therefore, PLEKHA7 stabilises both cadherins and nectins at AJ. [15]
Genome-wide association studies suggest that PLEKHA7 is associated with blood pressure and hypertension [16] [17] [18] [19] and primary angle closure glaucoma. [20] [21] [22] [23] [24] [25] [26] Also, an increased expression of PLEKHA7 in invasive lobular breast cancer has been reported. [27] In a more recent study, the expression of PLEKHA7 protein in high grade ductal breast carcinomas, and lobular breast carcinomas was found to be very low or undetectable by immunofluorescence or immunohistochemistry, despite the detection of PLEKHA7 mRNA [28] A Mayo Clinic study published online in August 2015 found that PLEKHA7 is mis-localized or lost in almost all breast and kidney tumor patient samples examined. [11]
Cadherins (named for "calcium-dependent adhesion") are cell adhesion molecules important in forming adherens junctions that let cells adhere to each other. Cadherins are a class of type-1 transmembrane proteins, and they depend on calcium (Ca2+) ions to function, hence their name. Cell-cell adhesion is mediated by extracellular cadherin domains, whereas the intracellular cytoplasmic tail associates with numerous adaptors and signaling proteins, collectively referred to as the cadherin adhesome.
Cell junctions or junctional complexes, are a class of cellular structures consisting of multiprotein complexes that provide contact or adhesion between neighboring cells or between a cell and the extracellular matrix in animals. They also maintain the paracellular barrier of epithelia and control paracellular transport. Cell junctions are especially abundant in epithelial tissues. Combined with cell adhesion molecules and extracellular matrix, cell junctions help hold animal cells together.
Catenins are a family of proteins found in complexes with cadherin cell adhesion molecules of animal cells. The first two catenins that were identified became known as α-catenin and β-catenin. α-Catenin can bind to β-catenin and can also bind filamentous actin (F-actin). β-Catenin binds directly to the cytoplasmic tail of classical cadherins. Additional catenins such as γ-catenin and δ-catenin have been identified. The name "catenin" was originally selected because it was suspected that catenins might link cadherins to the cytoskeleton.
Adherens junctions are protein complexes that occur at cell–cell junctions and cell–matrix junctions in epithelial and endothelial tissues, usually more basal than tight junctions. An adherens junction is defined as a cell junction whose cytoplasmic face is linked to the actin cytoskeleton. They can appear as bands encircling the cell or as spots of attachment to the extracellular matrix.
Catenin beta-1, also known as β-catenin (beta-catenin), is a protein that in humans is encoded by the CTNNB1 gene.
α-Catenin (alpha-catenin) functions as the primary protein link between cadherins and the actin cytoskeleton. It has been reported that the actin binding proteins vinculin and α-actinin can bind to alpha-catenin. It has been suggested that alpha-catenin does not bind with high affinity to both actin filaments and the E-cadherin-beta-catenin complex at the same time. It has been observed that when α-catenin is not in a molecular complex with β-catenin, it dimerizes and functions to regulate actin filament assembly, possibly by competing with Arp2/3 protein. α-Catenin exhibits significant protein dynamics. However, a protein complex including a cadherin, actin, β-catenin and α-catenin has not been isolated.
Afadin is a protein that in humans is encoded by the AFDN gene.
Poliovirus receptor-related 2 (PVRL2), also known as nectin-2 and CD112, is a human plasma membrane glycoprotein.
p120 catenin, or simply p120, also called catenin delta-1, is a protein that in humans is encoded by the CTNND1 gene.
Cadherin-3, also known as P-Cadherin, is a protein that in humans is encoded by the CDH3 gene.
Poliovirus receptor-related 1 (PVRL1), also known as nectin-1 and CD111 (formerly herpesvirus entry mediator C, HVEC) is a human protein of the immunoglobulin superfamily (IgSF), also considered a member of the nectins. It is a membrane protein with three extracellular immunoglobulin domains, a single transmembrane helix and a cytoplasmic tail. The protein can mediate Ca2+-independent cellular adhesion further characterizing it as IgSF cell adhesion molecule (IgSF CAM).
Receptor-type tyrosine-protein phosphatase beta or VE-PTP is an enzyme specifically expressed in endothelial cells that in humans is encoded by the PTPRB gene.
Receptor-type tyrosine-protein phosphatase mu is an enzyme that in humans is encoded by the PTPRM gene.
Cadherin-1 or Epithelial cadherin(E-cadherin), is a protein that in humans is encoded by the CDH1 gene. Mutations are correlated with gastric, breast, colorectal, thyroid, and ovarian cancers. CDH1 has also been designated as CD324. It is a tumor suppressor gene.
αE-catenin, also known as Catenin alpha-1 is a protein that in humans is encoded by the CTNNA1 gene. αE-catenin is highly expressed in cardiac muscle and localizes to adherens junctions at intercalated disc structures where it functions to mediate the anchorage of actin filaments to the sarcolemma. αE-catenin also plays a role in tumor metastasis and skin cell function.
VEZT is a gene located on chromosome 12 and encodes for the protein vezatin. Vezatin is a major component of the cadherin-catenin complex that is critical to the formation and maintenance of adherens junctions. The protein is expressed in most epithelial cells and is crucial to the formation of cell-cell contact junctions. Mutations of the gene can lead to upregulation or downregulation of the protein which can have detrimental effects on physiological systems, particularly those involved in development.
Lobular carcinoma in situ (LCIS) is an incidental microscopic finding with characteristic cellular morphology and multifocal tissue patterns. The condition is a laboratory diagnosis and refers to unusual cells in the lobules of the breast. The lobules and acini of the terminal duct-lobular unit (TDLU), the basic functional unit of the breast, may become distorted and undergo expansion due to the abnormal proliferation of cells comprising the structure. These changes represent a spectrum of atypical epithelial lesions that are broadly referred to as lobular neoplasia (LN).
Cingulin-like protein 1, also known as paracingulin or junction-associated-coiled-coil protein (JACOP), is a protein which is encoded by the CGNL1 gene.
Synaptic stabilization is crucial in the developing and adult nervous systems and is considered a result of the late phase of long-term potentiation (LTP). The mechanism involves strengthening and maintaining active synapses through increased expression of cytoskeletal and extracellular matrix elements and postsynaptic scaffold proteins, while pruning less active ones. For example, cell adhesion molecules (CAMs) play a large role in synaptic maintenance and stabilization. Gerald Edelman discovered CAMs and studied their function during development, which showed CAMs are required for cell migration and the formation of the entire nervous system. In the adult nervous system, CAMs play an integral role in synaptic plasticity relating to learning and memory.
Nectin-3, also known as nectin cell adhesion molecule 3, is a protein that in humans is encoded by the NECTIN3 gene.
