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Alpha 1-microglobulin (A1M) is a lipocalin superfamily member (kernal lipocalins). A1M is a low molecular weight protein component of plasma. A1M is distributed in plasma and extravascular compartments of all organs. Alpha-1 Microglobulin is found in mammals, birds, amphibians and fish. The primary sites of A1M synthesis are the liver and the kidney. Around the opening of the lipocalin pocket three lysyl residues are situated; those residues carry yellow-brown modification derived from the binding and degradation of heme and kynurenin (a tryptophan metabolite). A1-Microglobulin’s reductase and dehydrogenase have broad biological substrate specificity properties due to its’ free cysteine side-chain which is located in a flexible loop. Alpha-1-microglobulin is glycosylated by three separate carbohydrate chains: two complex carbohydrates which are N-linked to asparagines at residues 17 and 96, and the other simple carbohydrate which is O-linked to threonine at position 5. The carbohydrates comprise 22% of the total molecular mass of the protein. The glycosylation varies between species.
A1M exists in two forms- a free form and complexed to other macromolecules: in humans- complexed to immunoglobulin A (IgA), in rat- complexed to alpha-1-inhibitor-3. Free A1M is exceptionally heterogeneous in charge (therefore also known as protein HC), and is found tightly linked to a chromophore. The free Alpha-1-microglobulin is a monomeric protein composed of one 188 residue polypeptide and contains three cysteines, two of which (residues 75 and 173) form a conserved intra-molecular disulphide link. The chromophoric group is covalently bound to the free cysteine residue at position 34. A1M binds retinol as a major ligand, but this is probably distinct from its covalent chromophore.
Half of all human plasma A1M (approximately 0.03mg/ml) forms a 1:1 complex with about 5% of plasma immunoglobulin A. The resulting macromolecular complexes’ molecular weight is 200000, and a plasma concentration of 0.3mg/ml. The complex can exhibit both antibody activity and affect many of the biological actions of free Alpha-1-microglobulin.
Alpha-1-microglobulin was first discovered in pathological human urine.
It was suggested that A1M might be involved in tissue defense against reactive oxygen species, oxidation by heme and kynurenin. Evidence also suggests that A1M functions in the regulation of the immune system. Other functions include inhibition of stimulation of cultured lymphocytes by protein antigens; induction of cell division of lymphocytes, a mitogenic effect that can either be enhanced or inhibited by the action of other plasma components; inhibition of neutrophil granulocyte migration in vitro; and inhibition of chemotaxis.

Defensins form a family of microbicidal and cytotoxic peptides made by neutrophils. Members of the defensin family are highly similar in protein sequence. This gene encodes defensin, beta 103A, which has broad spectrum antimicrobial activity and may play an important role in innate epithelial defense.

Uteroglobin (SCGB1A1) which belongs to the Secretoglobin (SCGBs) superfamily, is a multifunctional protein that exerts anti-inflammatory and anti-tumorigenic effects by binding small hydrophobic molecules such as phospholipids and prostaglandins. Uteroglobin is involved in numerous functions including anti-inflammation, inhibition of phospholipase A2 and the sequestering of hydrophobic ligands. SCGB1A1 is expressed by Clara cells, the non-ciliated, non-mucous secretory cells predominant in lung bronchioles, and by other epithelia which communicate with the external environment. On top of sequestering pro-inflammatory mediators and carcinogens, Uteroglobin is implicated in the inhibition of cell migration and invasion, platelet aggregation, and T cell differentiation. SCGB1A1 gene defects are associated with a susceptibility to asthma.

PCBP1 is a single-stranded nucleic acid binding protein that binds preferentially to oligo dC. PCBP1 plays a role in formation of a sequence-specific alpha-globin mRNP complex which is associated with alpha-globin mRNA stability. PCBP1 along with PCBP-2 and hnRNPK corresponds to the major cellular poly(rC)-binding protein. PCBP1 and PCBP-2 also functions as translational coactivators of poliovirus RNA via a sequence-specific interaction with stem-loop IV of the IRES and promotes poliovirus RNA replication by binding to its 5'-terminal cloverleaf structure.

CXADR is a component of the epithelial apical junction complex which operates as an homophilic cell adhesion molecule and is crucial for tight junction integrity. CXADR also takes part in transepithelial relocation of leukocytes through adhesive interactions with AMICA1/JAML a transmembrane protein of the plasma membrane of leukocytes. A number of transcript variants encoding different isoforms were identified for this gene. Pseudogenes of this gene were located on chromosomes 15, 18, and 21.

PABPN1 is an highly expressed nuclear protein which has high affinity to nascent poly(A) tails. PABPN1 is essential for progressive and efficient polymerization of poly(A) tails at the 3' ends of eukaryotic transcripts and regulates the length of the poly(A) tail to about 250 nt. In its steady-state, PABPN1 is restricted to the nucleus however there are different poly(A) binding proteins which can be found in the cytoplasm. PABPN1 has a GCG trinucleotide repeat at the 5' end of the coding region. Expansion of this repeat from the normal 6 copies to 8-13 copies results in autosomal dominant oculopharyngeal muscular dystrophy (OPMD) disease. Associated pseudogenes were located on chromosomes 19 and X. Additionally, there is a read-through transcription between PABPN1 gene and the adjacent upstream BCL2L2 (BCL2-like 2) gene.

Protein Interacting with PRKCA 1, also known as PICK1 includes a PDZ domain, through which it interacts with protein kinase C, alpha (PRKCA). PICK1 performs as an adaptor which binds to and arranges the subcellular localization of various membrane proteins. PICK1 interacts with multiple glutamate receptor subtypes, monoamine plasma membrane transporters, in addition to non-voltage gated sodium channels, and might target PRKCA to these membrane proteins and therefore regulates their distribution as well as function. PICK1 has also been found to perform as an anchoring protein which particularly targets PRKCA to mitochondria in a ligand-specific manner.

Norrie Disease (NDP) is a secreted regulatory protein which activates the canonical Wnt signaling pathway through FZD4 and LRP5 coreceptor. NDP takes part in retinal vascularization by acting as a ligand for FZD4 which signals through stabilizing beta-catenin (CTNNB1) and activating LEF/TCF-mediated transcriptional programs. NDP is involved in a pathway that regulates neural cell differentiation and proliferation and also in neuroectodermal cell-cell interaction.

ERO1-like protein alpha (ERO1L) is an essential oxidoreductase, which oxidizes proteins and is necessary for the folding of immunoglobulins. ERO1L covalently binds with PDI (protein disulfide-isomerase) and jointly they generate disulfide bonds between proteins in the endoplasmic reticulum. ERO1L is stimulated by hypoxia, proposing that ERO1L is regulated through the HIF (hypoxia inducible transcrip-tion factor) pathway. At low levels ERO1L is ubiquitously expressed, however at high levels it is expressed in the upper digestive tract and esophagus. In addition, ERO1L is involved in the release of the unfolded cholera toxin from reduced P4HB/PDI in case of infection by V.cholerae, thus having a role in retrotranslocation of the toxin. Furthermore, ERO1L plays an important role in ER stress-induced, CHOP-dependent apoptosis by activating the inositol 1,4,5-trisphosphate receptor IP3R1.

MCM7 is a highly conserved mini-chromosome maintenance protein (MCM) vital for eukaryotic genome replication initiation. The MCM proteins form a hexameric protein complex which is a key component of the pre-replication complex (pre_RC) which takes part in replication forks formation and in DNA replication related proteins recruitment. The MCM complex is comprised of MCM2, 4, 6 and 7 proteins and possesses DNA helicase activity, such as DNA unwinding.

DNTTIP1 binds DNA and increases the activity of terminal deoxynucleotidyltransferase (TDT or DNTT), a DNA polymerase which catalyzes the polymerization of DNA in the absence of a DNA template.

JmjC domain-containing protein 7 (JMJD7) is a member of the JMJD family. JMJD7 encodes highly conserved proteins with a JmjC domain, which are part of the cupin metalloenzyme superfamily. JMJD7 was first thought to be an alternatively spliced isoform of PLA2G4B. It is derived from JMJD7 which is located upstream of PLA2G4B. Most tissues also express read-through transcripts from JMJD7 into the downstream PLA2G4B gene, some of which may encode fusion proteins combining the N-terminus of JMJD7 with PLA2G4B protein.

RAC1 is a GTPase which belongs to the RAS superfamily of small GTP-binding proteins. Members of this superfamily appear to regulate a diverse array of cellular events, including the control of cell growth, cytoskeletal reorganization, and the activation of protein kinases. RAC-1 regulates the actin cytoskeleton but also other cellular processes. RAC1 have been shown to be involved in the regulation of cell-cell adhesion.

CACYBP (calcyclin binding protein) participates in calcium-dependent ubiquitination and subsequent proteosomal degradation of target proteins. CACYBP acts as a molecular bridge in ubiquitin E3 complexes. CACYBP is involved in the ubiquitin-mediated degradation of beta-catenin.

Advanced Glycosylation End Product-Specific Receptor or RAGE is an immunoglobulin, part of the immunoglobulin transmembrane proteins family. RAGE moderates interactions between advanced glycosylation end products, also known as AGE. These signaling has a crucial part in the regulation of TNFalpha,oxidative stress, endothelial dysfunction in type 2 diabetesproduction and expression. RAGE helps the translocation of ABPP (amyloid-beta peptide) through the membrane of cells to the intracellular area in the cortical neurons.

MAX Dimerization Protein 3 (MXD3) belongs to the Myc superfamily of basic helix-loop-helix leucine zipper transcriptional regulators. MXD3 forms a heterodimer with the cofactor MAX that connects specific E-box DNA motifs in the promoters of target genes and regulates their transcription. Disturbance of the MAX-MXD3 complex is correlated with uncontrolled cell proliferation and tumorigenesis. Transcript variants of MXD3 encoding different isoforms have been described.

BDNF promotes the survival of neuronal populations that are all located either in the central nervous system or directly connected to it. BDNF is a major regulator of synaptic transmission and plasticity at adult synapses in many regions of the cns. The versatility of BDNF is emphasized by its contribution to a range of adaptive neuronal responses including long-term potentiation (ltp), long-term depression (ltd), certain forms of short-term synaptic plasticity, as well as homeostatic regulation of intrinsic neuronal excitability.

MAP1LC3B is a member of the MAP1 LC3 family. MAP1LC3B is a subunit of neuronal microtubule-associated MAP1A and MAP1B proteins, that are involved in microtubule assembly and important for neurogenesis. In addition, MAP1LC3B takes part in formation of autophagosomal vacuoles and is expressed mainly in heart, testis, brain and skeletal muscle.

Killer Cell lectin-Like Receptor Subfamily K, Member 1 (KLRK1) is an activating receptor which has recently generated considerable interest. The most fascinating of these, are a couple of closely related proteins known as MICA and MICB. These are cell-surface molecules distantly related to MHC class I proteins, and their genes have elements of heat shock promoters. Thus, MICA and MICB are expressed in the course of cell stress and are up-regulated in tumor cells and during viral infections. This receptor-ligand combination has a crucial role in the immune response to various pathologies.

SUMO1 is a protein that belongs to the SUMO (small ubiquitin-like modifier) protein family. SUMO1 functions in a manner similar to ubiquitin in that it is bound to target proteins as part of a post-translational modification system. Still, unlike ubiquitin which targets proteins for degradation, SUMO1 is involved in a variety of cellular processes, for example nuclear transport, transcriptional regulation, apoptosis, and protein stability. SUMO1 is not active until the last four amino acids of the carboxy-terminus are cleaved off.

GDP Dissociation Inhibitor 1 (GDI1) is expressed mainly in neural and sensory tissues. GDI1 regulates the GDP/GTP exchange reaction of nearly all Rab proteins by inhibiting the dissociation of GDP from them, and the subsequent binding of GTP to them. GDI1 is also promoting the dissociation of GDP-bound Rab proteins from the membrane and inhibits their activation. Mutations in GDI1 have been associated with X-linked nonspecific mental retardation.

Mitogen-activated protein kinase 1 (MAPK1) is also known as "extracellular signal-regulated kinase 2" (ERK2). Two similar (85% sequence identity) protein kinases were originally called ERK1 and ERK2. They were found during a search for protein kinases that are rapidly phosphorylated after activation of cell surface tyrosine kinasessuch as the epidermal growth factor receptor. Phosphorylation of ERKs leads to the activation of their kinase activity. The molecular events linking cell surface receptors to activation of ERKs are complex. It was found that RasGTP-binding proteins are involved in the activation of ERKs. Another protein kinase, Raf-1, was shown to phosphorylate a "MAPK kinase", thus qualifying as a "MAPK kinase kinase". The MAPK kinase was named "MAPK/ERK kinase" (MEK). Receptor-linked tyrosine kinases, Ras, Raf, MEK and MAPK could be fitted into a signaling cascade linking an extracellular signal to MAPK activation. Transgenic gene knockoutmice lacking MAPK1 have major defects in early development.

Programmed cell death 1 ligand 2 (PDCD1LG2) which takes part in the costimulatory signal, is necessary for T-cell proliferation. PDCD1LG2 is also involved in IFNG production in a PDCD1-independent way. The interaction with PDCD1 inhibits T-cell proliferation by preventing cytokine production and cell cycle progression.

DNAL4 is a member of the dynein light chain family. DNAL4 is a component of the dynein motor complex in cells that converts the chemical energy contained in ATP into the mechanical energy of movement. Dynein transports various cellular cargos by moving the length of cytoskeletal microtubules towards the minus-end of the microtubule, which is typically oriented towards the cell center.