Nectin-3, also known as nectin cell adhesion molecule 3, is a protein that in humans is encoded by the NECTIN3 gene.
Nectin-3 belongs to the family of immunoglobulin(Ig)-like cellular adhesion molecules involved in Ca2+-independent cellular adhesion [5] in several tissues during the development [6] and was firstly isolated at the turn of 20th and 21st century. [7]
Nectin-3 has three splicing variants, nectin-3α, which is the biggest one, nectin-3β and the smallest variant nectin-3γ.
Nectin-3α (same as the other splicing variants) is abundately expressed in testis, on slightly lower level it is also expressed in heart, brain, liver or kidney. It has been also proved that nectin-3α is together with nectin-2 localize at the junctional complex regions in small intestina absorptive epitelia. Nectin-3γ is also detectable in lung, liver and kidney. [7] Nectin-3 is expressed not only on epithelial cells as another nectins, but there was shown that, as the only member of nectin family, it is expressed also on T- lymphocytes. [8]
The structural properties of nectin-3α is similar to nectin-1, it has three Ig-like domains at the extracellular region and the C-terminal conserved motif at the cytoplasmic region. The homology of aa (amino aci)) of extracellular domains between Nectin-1 and Nectin-3α is 35,9%. Another splicing variants vary in the number of aa, molecular weight and the structural properties. All of them have the identical extracellular region. Nectin-3β and nectin-3γ have the same transmembrane and cytoplasmic regions, which vary from nectin-3α. Nectin-3γ lack of C-terminal domain. [7] With the intracellular domain nectins bind their assosicated adaptor protein afadin [9] which plays role in the formation of variety of cell-cell junctions. [10] Nectin-3γ in not able to bind afadin due to lacking C-terminal domain. [7]
All nectins are able to form cis-homo dimer interactions, which simply means they can create dimer of two alike molecules on the same cell membrane. Further, nectin-3α can also interact with Nectin-1/2α in so called trans-hetero interaction. [7]
Most of the publications deal with nectin-3 regardless the splicing variants, thus this page follows this concept.
Nectin-3 is expressed by granule cells in dentate gyrus and the expression levels are developmentally regulated and reduced by early postnatal stress. On mice model, it has been shown that the early-life stress impaires the long-term spatial memory and temporal order memory. It is also very probable that the nectin-3 in dentate gyrus neurons modulate adult neurogenesis and dendritic spine plasticity. [11] It has been proven that combination nectin-3/nectin-1 is very important in formation of synapses in brain, hippocampus and that the formation of hetero-trans-dimers between nectin-1 and nectin-3 determines the position and size of the synapses, in vitro . [12] In vivo , it has been shown that the function of nectin-3 is crutial during the critical periods of the visual cortex development and that it is important not only for synapses formation but also for the synaptic refinement. Also it has been proven that there is a high importance of nectin-3 for the dendritic spine densities (which simply represent the sites of synaptic contacts) on visual cortical neurons. [13] The nectin-1/nectin-3 trans-interaction has been shown to be very important to establishing the adhesion between the pigment and non-pigment cell layers of the ciliary epithelia, which is essential for the morphogenesis of the ciliary body of the eye. [14]
Nectin-3 is important role player in spermatid development. The nectin-3–/– male mice were found to have defects in the later steps of sperm morphogenesis, exhibiting distorted nuclei and abnormal distribution of mitochondria. The loss of nectin-3 in male mice leads to male-specific infertility. [15] It has been shown that the chronic stress negatively influences the amnout of nectin-3 in the testis and also the male spermatogenesis function. [16]
As mentioned above, nectin-3 is the only nectin which is expressed on T- lymphocytes. The interaction between nectin-3 on T-cells and other nectins on epithelial cells is very important in the lymphocyte transendothelial migration, in vitro. It has been shown that this process is dependent on nectin-2, which is expressed on epithelial cells, the blockation of nectin-2 or nectin-3 leads to inhibition of lymphocyte and also monocyte extravasation. [17]
Nectin-3 is highly expressed in epithelial cancer cells of human lung adenocarcinoma. It is expressed in 80% of patients which makes it relatively strong prognostic marker. It has been shown, there are various expression patterns of nectin-3; cytoplasmic, membranous or combined. The membranous expression is connected with significantly poorer prognosis, patients with this type of expression pattern are also more likely to earlier relapse and death. [18] Increased amounts of nectin-3 are also detectable in ovaries during the ovarian cancer and are correlated with poor patient prognosis. The data also suggest that the possible mechanism of nectin-3 in cellular invasion and migration is by upregulating the expression of matrix metalloproteinases (MMPs) MMP2 and MMP9 in ovarian cancer. [19]
Contrary to previously mentioned cancers, the amount of nectin-3 negatively correlates with Pancreatic neuroendocrine tumors. The loss of this protein correlates with increased tumor progressiveness. [20]
Nectin-3 has been shown to interact with:
Measles morbillivirus(MeV), also called measles virus (MV), is a single-stranded, negative-sense, enveloped, non-segmented RNA virus of the genus Morbillivirus within the family Paramyxoviridae. It is the cause of measles. Humans are the natural hosts of the virus; no animal reservoirs are known to exist.
L1, also known as L1CAM, is a transmembrane protein member of the L1 protein family, encoded by the L1CAM gene. This protein, of 200-220 kDa, is a neuronal cell adhesion molecule with a strong implication in cell migration, adhesion, neurite outgrowth, myelination and neuronal differentiation. It also plays a key role in treatment-resistant cancers due to its function. It was first identified in 1984 by M. Schachner who found the protein in post-mitotic mice neurons.
Platelet endothelial cell adhesion molecule (PECAM-1) also known as cluster of differentiation 31 (CD31) is a protein that in humans is encoded by the PECAM1 gene found on chromosome17q23.3. PECAM-1 plays a key role in removing aged neutrophils from the body.
The CD44 antigen is a cell-surface glycoprotein involved in cell–cell interactions, cell adhesion and migration. In humans, the CD44 antigen is encoded by the CD44 gene on chromosome 11. CD44 has been referred to as HCAM, Pgp-1, Hermes antigen, lymphocyte homing receptor, ECM-III, and HUTCH-1.
L-selectin, also known as CD62L, is a cell adhesion molecule found on the cell surface of leukocytes, and the blastocyst. It is coded for in the human by the SELL gene. L-selectin belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups containing a Sialyl LewisX (sLeX) determinant. L-selectin plays an important role in both the innate and adaptive immune responses by facilitating leukocyte-endothelial cell adhesion events. These tethering interactions are essential for the trafficking of monocytes and neutrophils into inflamed tissue as well as the homing of lymphocytes to secondary lymphoid organs. L-selectin is also expressed by lymphoid primed hematopoietic stem cells and may participate in the migration of these stem cells to the primary lymphoid organs. In addition to its function in the immune response, L-selectin is expressed on embryonic cells and facilitates the attachment of the blastocyst to the endometrial endothelium during human embryo implantation.
Macrophage Inflammatory Proteins (MIP) belong to the family of chemotactic cytokines known as chemokines. In humans, there are two major forms, MIP-1α and MIP-1β, renamed CCL3 and CCL4 respectively, since 2000. However, other names are sometimes encountered in older literature, such as LD78α, AT 464.1 and GOS19-1 for human CCL3 and AT 744, Act-2, LAG-1, HC21 and G-26 for human CCL4. Other macrophage inflammatory proteins include MIP-2, MIP-3 and MIP-5.
CD146 also known as the melanoma cell adhesion molecule (MCAM) or cell surface glycoprotein MUC18, is a 113kDa cell adhesion molecule currently used as a marker for endothelial cell lineage. In humans, the CD146 protein is encoded by the MCAM gene.
Discs large homolog 1 (DLG1), also known as synapse-associated protein 97 or SAP97, is a scaffold protein that in humans is encoded by the SAP97 gene.
Afadin is a protein that in humans is encoded by the AFDN gene.
Intercellular adhesion molecule 2 (ICAM2), also known as CD102, is a human gene, and the protein resulting from it.
Signal regulatory protein α (SIRPα) is a regulatory membrane glycoprotein from SIRP family expressed mainly by myeloid cells and also by stem cells or neurons.
Cell adhesion molecule 1 is a protein that, in humans, is encoded by the CADM1 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).
Junctional adhesion molecule B is a protein that in humans is encoded by the JAM2 gene. JAM2 has also been designated as CD322.
CD226, PTA1 or DNAM-1 is a ~65 kDa immunoglobulin-like transmembrane glycoprotein expressed on the surface of natural killer cells, NK T cell, B cells, dendritic cells, hematopoietic precursor cells, platelets, monocytes and T cells.
Disks large-associated protein 2 is a protein that in humans is encoded by the DLGAP2 gene.
Cell adhesion molecule 3 is a protein that in humans is encoded by the CADM3 gene.
Nectins and Nectin-like molecules (Necl) are families of cellular adhesion molecules involved in Ca2+-independent cellular adhesion.
CD96 or Tactile is a protein that in humans is encoded by the CD96 gene. CD96 is a receptor protein which is expressed on T cells and NK cells and shares sequence similarity with CD226. The protein encoded by this gene belongs to the immunoglobulin superfamily. It is a type I membrane protein. The protein may play a role in the adhesion of activated T and NK cells to their target cells during the late phase of the immune response. It may also function in antigen presentation. Alternative splicing occurs at this locus and two transcript variants encoding distinct isoforms have been identified. CD96 is a transmembrane glycoprotein that has three extracellular immunoglobulin-like domains and is expressed by all resting human and mouse NK cells. CD96 main ligand is CD155. CD 96 has approximately 20% homology with CD226 and competed for binding to CD155 with CD226.
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.