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Keratin 8 and 18 (K8/18) are the major components of intermediate filament (IF) proteins of simple or single-layered epithelia.

Cytohesin 3 (CYTH3) belongs to the PSCD family, whose members have identical structural organization which consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain, and seem to mediate the regulation of protein sorting and membrane trafficking. CYTH3 is involved in the regulation of Golgi structure and function, and it might have a physiological role in regulating ADP-ribosylation factor protein 6 (ARF) functions, in addition to acting on ARF1.

Killer Cell Lectin-like Receptor Subfamily G, Member 1 (KLRG1) is a member of the killer cell lectin-like receptor (KLR) family, which is a group of transmembrane proteins preferentially expressed in NK cells. Natural killer (NK) cells are lymphocytes which mediate lysis of certain tumor cells and virus-infected cells without previous activation. NK cells can also regulate specific humoral and cell-mediated immunity. The cell surface expression of KLRG1 is up-regulated by MHC class I molecules expression.

Killer cell lectin-like receptor subfamily F member 1, aka KLRF1, is a member of the C-type lectin family. KLRF1, an activating homodimeric C-type lectin-like receptor (CTLR), is expressed on nearly all natural killer (NK) cells and stimulates their cytoxicity and cytokine release. Killer cell lectin-like receptor subfamily F member 1 works through interaction with its ligand, AICL (activation-induced C-type lectin), which is selectively expressed on myeloid cells. AICL interaction regulates the immune responses at sites of inflammation by stimulating the release of proinflammatory cytokines. Diseases associated with KLRF1 include Developmental And Epileptic Encephalopathy 76.

Chloride channels are various group of proteins that control fundamental cellular processes including stabilization of cell membrane potential, transepithelial transport, regulation of intracellular pH, and maintenance of cell volume. CLIC1 is part of the p64 family and is localized to the cell nucleus. CLIC1 displays both nuclear and plasma membrane chloride ion channel activity. CLIC1 inserts into membranes and forms chloride ion channels. CLIC1 channel activity depends on the pH. CLIC1 membrane insertion is redox-regulated and happens under oxydizing conditions.

Chloride intracellular channel protein 2 (CLIC2) regulates cellular traffic of chloride ions, which is a critical component of all living cells. CLIC2 is involved in membrane potential stabilization, signal transduction, cell volume regulation and organic solute transport. CLIC2 is identified in the fetal liver and adult skeletal muscle tissue. CLIC2 is a likely candidate for one of the many diseases linked to Xq28.

Cytokeratin 8 (KRT8) belongs to the type II keratin family clustered on the long arm of chromosome 12. Type I and type II keratins heteropolymerize to form intermediate-sized filaments in the cytoplasm of epithelial cells. KRT8 typically dimerizes with keratin 18 to form an intermediate filament in simple single-layered epithelial cells. KRT8 has a role in retaining cellular structural integrity and also functions in signal transduction and cellular differentiation. KRT8 gene mutations cause cryptogenic cirrhosis.

Chloride intracellular channel 4 (CLIC4) belongs to the p64 family; CLIC4 is expressed in various tissues and exhibits an intracellular vesicular pattern in Panc-1 cells (pancreatic cancer cells). CLIC4 is a 253 amino acid single-pass membrane protein which localizes to both the nucleus and the cytoplasm and contains one GST C-terminal domain. CLIC4 acts as a monomer which is able to form selective ion channels in target proteins, thus facilitating the transport of chloride and other ions. CLIC4 is believed to have a role in apoptosis and is able to translocate to the nucleus under stress conditions.

CTK-19 is a member of the keratin family. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. The type I cytokeratins consist of acidic proteins which are arranged in pairs of heterotypic keratin chains. Unlike its related family members, this smallest known acidic cytokeratin is not paired with a basic cytokeratin in epithelial cells. It is specifically expressed in the periderm, the transiently superficial layer that envelopes the developing epidermis. The type I cytokeratins are clustered in a region of chromosome 17q12-q21.

Sclerostin (SOST) is a secreted glycoprotein with a C-terminal cysteine knot-like (CTCK) domain and sequence similarity to the DAN (differential screening-selected gene aberrative in neuroblastoma) family of bone morphogenetic protein antagonists. Sclerostin functions as a negative regulator of bone growth, by inhibiting bone formation. SOST is expressed mainly in the bone, cartilage, kidney, liver, bone marrow and primary osteoblasts differentiated for 21 days. SOST gene defects cause sclerosteosis and bone dysplasia.

Pleckstrin homology-like domain family A member 2 (PHLDA2) is a cytoplasmic protein, which is involved in fetal and placental growth. PHLDA2 is an apoptosis-related protein, which acts as a negative growth regulator and is expressed during normal human development. PHLDA2 is imprinted on placenta, liver and fetal tissues during embryogenesis and is removed once development is complete. The PHLDA2 gene is one of a number of genes in the imprinted gene domain of 11p15.5 which is considered to be an important tumor suppressor gene region. Changes in this region may be linked to the Beckwith-Wiedemann syndrome, Wilms tumor, rhabdomyosarcoma, adrenocortical carcinoma, and lung, ovarian, and breast cancer. PHLDA2 is expressed in placenta (present in all cells of the villous cytotrophoblast) and adult prostate gland. Furthermore, PHLDA2 is expressed in adult brain and neuroblastoma, medullablastoma and glioblastoma cell lines and at low levels in adult liver and lung, and fetal liver.

Cathepsin D is synthesized as a 54kDa precursor, which is proteolytically processed to an intermediate 48kDa single chain, which matures into more stable 34kDa and 14kDa two chain form. It is an estrogen-regulated lysosomal protease that has been suggested to facilitate cancer cell migration and invasion by digesting the basement membrane, extracellular matrix, and xonnective tissue. Because of its mitogenic and proteolytic activities, it has been implicated as a prognostic marker in many tumor types. Cathepsin D is expressed in epithelial cells as well as in macrophages.

KLRC3 belongs to the NKG2 group that can be found mostly in natural killer (NK) cells and encodes a family of transmembrane proteins known for their C-type lectin domain and their type II membrane orientation (extracellular C terminus). The NKG2 gene family is situated inside the NK complex, a region which has quite a few C-type lectin genes mostly expressed on NK cells.

Frataxin is a mitochondrial iron binding protein that is part of the FRATAXIN family. Frataxin functions in regulating mitochondrial iron transport and respiration. The expansion of intronic trinucleotide repeat GAA results in Friedreich ataxia. Frataxin plays a role in iron homeostasis. Frataxin is an anti-apoptotic protein which prevents mitochondrial damage and reactive oxygen species (ROS) production.

Clusterin also named Apolipoprotein J (APO-J) is a 75-80 kD disulfide-linked heterodimeric protein containing about 30% of N-linked carbohydrate rich in sialic acid but truncated forms targeted to the nucleus have also been identified.
The precursor polypeptide chain is cleaved proteolytically to remove the 22-mer secretory signal peptide and subsequently between residues 227/228 to generate the a and b chains. These are assembled in anti-parallel to give a heterodimeric molecule in which the cysteine-rich centers are linked by five disulfide bridges and are flanked by two predicted coiled-coil a-helices and three predicted amphipathic a-helices.
Across a broad range of species clusterin shows a high degree of sequence homology ranging from 70% to 80%. It is nearly ubiquitously expressed in most mammalian tissues and can be found in plasma, milk, urine, cerebrospinal fluid and semen.
It is able to bind and form complexes with numerous partners such as immunoglobulins, lipids, bacteria, complement components, paraoxonase, beta amyloid, leptin and others. Clusterin has been ascribed a plethora of functions such as phagocyte recruitment, aggregation induction, complement attack prevention, apoptosis inhibition, membrane remodeling, lipid transport, hormone transport and/or scavenging, matrix metalloproteinase inhibition.
A genuine function of clusterin has not been defined. One tempting hypothesis says that clusterin is an extracellular chaperone protecting cells from stress induced insults caused by degraded and misfolded protein precipitates.
Clusterin is up- or down regulated on the mRNA or protein level in many pathological and clinically relevant situations including cancer, organ regeneration, infection, Alzheimer disease, retinitis pigmentosa, myocardial infarction, renal tubular damage, autoimmunity and others.

Mammalian crystallins which are water soluble structural proteins located in the vertebrate eye are classified in three forms, labeled alpha, beta and gamma. Crystallins, the primary components of the lens, raise the refractive index of the eye all through the accommodation by creating high-molecular weight aggregates that maintain transparency. CRYGS is a monomer that does not aggregate. CRYGS encodes the most substantial gamma-crystallin in adult eye lens tissue. Gamma-crystallins has a part in cataract formation due to aging or mutations in specific genes,

E-cadherin (uvomorulin, cell-CAM120/80) is a calcium dependent cell adhesion molecule expressed predominately in epithelial tissues. It plays an important role in the growth and development of cells via the mechanisms of control of tissue architecture and the maintenance of tissue integrity. Numerous studies have demonstrated that reduction and/or loss of Ecadherin expression in carcinomas correlates positively with the potential of these tumors for invasion and metastasis.

CTLA-4 is a member of the immunoglobulin superfamily and encodes a protein which transmits an inhibitory signal to T cells. The protein contains a V domain, a transmembrane domain, and a cytoplasmic tail. Alternate transcriptional splice variants, encoding different isoforms, have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond, while the soluble isoform functions as a monomer. Mutations in this gene have been associated with insulin-dependent diabetes mellitus, Graves disease, Hashimoto thyroiditis, celiac disease, systemic lupus erythematosus, thyroid-associated orbitopathy, and other autoimmune diseases.

Platelet factor-4 is a 70-amino acid protein that is released from the alpha-granules of activated platelets. Its major physiologic role appears to be neutralization of molecules on the endothelial surface of blood vessels, thereby inhibiting local activity and promoting coagulation. As a strong chemoattractant for neutrophils and fibroblasts, PF4 probably has a role in inflammation and wound repair. Oncostatin-A is a member of the CXC chemocinfamily.

Platelet factor-4 is a 70-amino acid protein that is released from the alpha-granules of activated platelets and binds with high affinity to heparin. Its major physiologic role appears to be neutralization of heparin-like molecules on the endothelial surface of blood vessels, thereby inhibiting local antithrombin III activity and promoting coagulation. As a strong chemoattractant for neutrophils and fibroblasts, PF4 probably has a role in inflammation and wound repair. Oncostatin-A is a member of the CXC chemokine family. Human PF4 is used for the proof of heparin-induced thrombocytopenia. Furthermore it is used as an inhibitor in the angiogenesis during tumor therapy.

CD207 (C-type lectin domain family 4 member K) is expressed in Langerhans cells which are immature dendritic cells of the epidermis and mucosa. Moreover, CD207 is expressed in several other dendritic cell types including dermal CD103+ DCs and splenic CD8+ DCs. Langerin is localized in the Birbeck granules, the organelles present in the cytoplasm of Langerhans cells and comprised of superimposed and zippered membranes. CD207 is a C-type lectin with mannose binding specificity, and it has been suggested that mannose binding by the CD207 protein leads to internalization of antigen into Birbeck granules thus providing access to a nonclassical antigen-processing pathway.

CTK-19 is a member of the keratin family. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. The type I cytokeratins consist of acidic proteins which are arranged in pairs of heterotypic keratin chains. Unlike its related family members, this smallest known acidic cytokeratin is not paired with a basic cytokeratin in epithelial cells. It is specifically expressed in the periderm, the transiently superficial layer that envelopes the developing epidermis. The type I cytokeratins are clustered in a region of chromosome 17q12-q21.

Killer Cell Lectin-Like Receptor Subfamily C, Member 1 (KLRC1) is a part of the killer cell lectin-like receptor family. KLRC1 functions as a receptor for the detection of MHC class I HLA-E molecules by NK cells and some cytotoxic T-cells. KLRC1 is also connects with CD94 and is expressed on NK cells and some activated T cell.