Complement is defined as key part of innate immunity and as the first line of defense in the fight against invading pathogens. Complement 3 (C3) is the most abundant component of the complement cascade and the convergent point for all three major complement activation pathways: namely classical, alternative and mannose-binding lectin pathways. Complement activation leads to the formation of the C3 convertase, which cleaves C3 into the key effector molecules, C3a (anaphylatoxin) and C3b (opsonin) which then drive microbe removal. By binding to C3a receptor (C3aR), C3a exhibits potent anaphylatoxin activity, including increased vascular permeability, triggering degranulation of mast cells, inflammation, and activating leukocytes.
Contactins are a subgroup of molecules belonging to the immunoglobulin superfamily that are expressed exclusively in the nervous system. The subgroup consists of six members: Contactin-1, Contactin-2 (TAG-1), Contactin-3 (BIG-1), BIG-2, Contactin-5 (NB-2) and NB-3. Axonal expression and the neurite extension activity of Contactin-1 and Contactin-2 attracted researchers to study the function of these molecules in axon guidance during development. Contactin-1 and Contactin-2 have come to be known as the principal molecules in the function and maintenance of myelinated neurons. In contrast, the function of the other four members of this subgroup remained unknown until recently. Contactin-1 is a cell surface adhesion molecule that is normally expressed by neurons and oligodendrocytes. Particularly high levels of Contactin-1 are present during brain development. Contactin-1 and Contactin-2 are differentially expressed in a number of neuronal tissues during development, and they interact with several ligands including Nr-CAM, L1, NCAM, neurocan, phosphacan, and tenascin. As a cell adhesion molecule, Contactin-1 plays a role in the formation of axon connections in the developing nervous system. It was demonstrated that Contactin-1 participates in signal pathways via its association with Contactin-associated protein (CNTNAP1), receptor protein tyrosine phosphatase beta (RPTPb) and NOTCH1. Contactin-1 is also involved in paranodal axo-glial junction formation and oligodendrocytes generation.
Contactins are a subgroup of molecules belonging to the immunoglobulin superfamily that are expressed exclusively in the nervous system. The subgroup consists of six members: Contactin-1, Contactin-2(TAG-1), Contactin-3(BIG-1), BIG-2, Contactin-5(NB-2) and NB-3. Axonal expression and the neurite extension activity of Contactin-1 and Contactin-2 attracted researchers to study the function of these molecules in axon guidance during development. Contactin-1 and Contactin-2 have come to be known as the principal molecules in the function and maintenance of myelinated neurons. Contactin-2, also known as CNTN2, is a glycosylphosphatidylinositol (GPI)-anchored neuronal membrane protein that functions as a cell adhesion molecule. Contactin-2 is expressed by a subset of neuronal populations in the developing central nervous system (CNS) and peripheral nervous system (PNS). Contactin-2 is also expressed by oligodendrocytes and Schwann cells, which are myelinating glial cells of the CNS and PNS, respectively. Contactin-2 may play a role in the formation of axon connections in the developing nervous system. Contactin-2 is also involved in glial tumorigenesis and may provide a potential target for therapeutic intervention. During embryonic development, Contactin-2 interacts either in a homophilic, or heterophilic fashion with various transmembrane proteins.
Contactins are a subgroup of molecules belonging to the immunoglobulin superfamily that are expressed exclusively in the nervous system. The subgroup consists of six members: Contactin-1, Contactin-2(TAG-1), Contactin-3(BIG-1), BIG-2, Contactin-5(NB-2) and NB-3. Since their identification in the late 1980s, Contactin-1 and Contactin-2 have been studied extensively. Axonal expression and the neurite extension activity of Contactin-1 and Contactin-2 attracted researchers to study the function of these molecules in axon guidance during development. Contactin-1 and Contactin-2 have come to be known as the principal molecules in the function and maintenance of myelinated neurons. In contrast, the function of the other four members of this subgroup remained unknown until recently. Contactin-3, also known as CNTN3 ( BIG-1 in rat and PANG in mouse ), is a GPI-linked glycoprotein that is expressed on cerebellar Purkinje cells, amygdaloid and thalamic neurons and olfactory granule cells. In the brain, Contactin-3 is expressed in frontal lobe, occipital lobe, cerebellum and amygdala. Contactin-3 contains 4 fibronectin type-III domains and 6 Ig-like C2-type (immunoglobulin-like) domains. Human Contactin-3 shares 92% aa identity with mouse Contactin-3.The exact function of Contactin-3 is unclear. Contactin-3 may mediate cell-cell interaction and may promote neurite outgrowth.
Contactins are a subgroup of molecules belonging to the immunoglobulin superfamily that are expressed mainly in the nervous system. The subgroup consists of six members: Contactin-1, Contactin-2(TAG-1), Contactin-3(BIG-1), BIG-2, Contactin-5(NB-2) and NB-3. Since their identification in the late 1980s, Contactin-1 and Contactin-2 have been studied extensively. Axonal expression and the neurite extension activity of Contactin-1 and Contactin-2 attracted researchers to study the function of these molecules in axon guidance during development. Contactin-1 and Contactin-2 have come to be known as the principal molecules in the function and maintenance of myelinated neurons. In contrast, the function of the other four members of this subgroup remained unknown until recently. Contactin-5, also known as NB-2, is one of the neural recognition molecules in the contactin subgroup. Contactin-5 is expressed in brain and kidney and at very low level in placenta. In brain, Contactin-5 is highly expressed in the occipital lobe, amygdala, cerebral cortex, frontal lobe, thalamus and temporal lobe. Mice deficient in the Contactin-5 gene exhibit aberrant responses to acoustic stimuli. Contactin-5 may play a role in maturation of glutamatergic synapses in the brainstem during the final stages of auditory development. Contactin-5 gene may contribute to human neurological disorders.
Carboxypeptidase A2 ( CPA2 ) is a secreted pancreatic procarboxy -peptidase, and cleaves the C-terminal amide or ester bond of peptides that have a free C-terminal carboxyl group. The hydrolytic action of CPA2 was identified with a preference towards long substrates with aromatic amino acids in their C-terminal end, particularly tryptophan. CPA2 comprises a signal peptide, a pro region and a mature chain, and can be activated after cleavage of the pro peptide. Three different forms of human pancreatic procarboxypeptidase A have been isolated, and the A1 and A2 forms are always secreted as monomeric proteins with different biochemical properties.
Mouse carboxypeptidase A2(CPA2) is a secreted pancreatic procarboxy -peptidase which belongs to the peptidase M14 family. CPA2 consists of a signal peptide, a pro region and a mature chain. It can be activated after cleavage of the pro peptide. CPA2 cleaves the C-terminal amide or ester bond of peptides that have a free C-terminal carboxyl group. The hydrolytic action of CPA2 was identified with a preference towards long substrates with aromatic amino acids in their C-terminal end, particularly tryptophan.
Carboxypeptidase Q (Cpq) is a member of the peptidase M28 family. PGCP is involved in a number of fundamental biological processes such as the hydrolysis of circulating peptides, catalyzing the hydrolysis of dipeptides with unsubstituted terminals into amino acids. Carboxypeptidase may play an important role in the liberation of thyroxine hormone from its thyroglobulin (Tg) precursor. The monomeric form is inactive while the homodimer is active.
Cellular retinoic acid-binding protein 2, also known as Cellular retinoic acid-binding protein II, CRABP-II and CRABP2, is a protein which belongs to thecalycin superfamily and Fatty-acid binding protein (FABP) family. Cellular retinoic acid binding proteins (CRABP) are low molecular weight proteins whose precise function remains unknown. The predicted amino acid sequences of human CRABP1 and CRABP2 demonstrated a 99.3% and 93.5% identity to mouse CRABP1 and CRABP2, respectively. CRABP2 forms a beta-barrel structure that accommodates hydrophobic ligands in its interior. Expression of CRABP2, but not CRABP1 mRNA, was markedly increased (greater than 15-fold) by retinoic acid treatment of fibroblasts cultured from human skin, whereas no significant induction of CRABP2 mRNA was observed in human lung fibroblasts. CRABP2 transports retinoic acid to the nucleus. It regulates the access of retinoic acid to the nuclear retinoic acid receptors. CRABP2 is necessary for elastin induction by All-trans retinoic acid (ATRA) in MRC-5 cells. It is expressed at low levels in emphysema fibroblasts. This alteration in the retinoic acid signalling pathway in lung fibroblasts may contribute to the defect of alveolar repair in human pulmonary emphysema.
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