M= Mouse; R=Rat; H=Human; Rb=Rabbit; G=goat; B=Bovine, MO=Monkey; P=pig; CT= near C-terminus; NT=near N-terminus; Internal=Middle of protein. EC=extracellular; CP=cytoplasmic domains *

 
Pentraxins (PTX3) and Neuronal Pentraxins (NPX1-2) Antibodies

Pentraxins are a family of proteins emerging from genes that are conserved in their carboxy-terminal halves a pentraxin domain and are prototypical acute phase proteins with acquired novel amino-terminal domains. Pentraxins, include C reactive protein (CRP) and Serum Amyloid P component (SAP), which serve as indicators of inflammatory reactions as a result of the exposure of liver cells to cytokines, mainly interleukin-6 (IL-6).

CRP is defined as a substance, observed in the plasma of patients with acute infections that reacted with the C polysaccharide of the pneumococcus. It is one of the plasma proteins that are called acute phase reactants because of a pronounced rise in concentration after tissue injury or inflammation; in the case of CRP the rise may be 1000-fold or more. CRP is composed of 5 identical, 21,500-molecular weight subunits. It is detectable on the surface of about 4% of normal peripheral blood lymphocytes. Acute phase reactant CRP is produced in the liver; those cells produce CRP detectable on lymphocytes.

Serum amyloid P component or SAP or APCS, or PTX2, a constitutive serum glycoprotien (mature chain 204 aa, chromosome 1q21-23) with which CRP has about 59% homology, is situated in the same area of chromosome 1. SAP binds to the collagen-like region of C1q and activates the classical complement pathway. It binds to C4b-binding protein (C4bp) and prevents the factor I-mediated inactivation of C4b. It also binds to extracellular matrix (ECM) components such as type IV collagen, fibronectin, and proteoglycans. In mice with a targeted deletion of the SAP gene, induction of reactive amyloidosis was retarded, demonstrating the participation of SAP in pathogenesis of amyloidosis in vivo and confirming that inhibition of SAP binding to amyloid fibrils is an attractive therapeutic target. SAP is a component of all amyloid plaques and is also a normal component of a number of basement membranes including the glomerular basement membrane.

PTX3 or TSG14 or long pentraxin (human mature chain 364 aa, chromosome 3q25; ~43 kDa) is structurally related but different form classic pentraxins. PTX3 was clones as an IL-1 inducible gene in endothelial cells, and as TNF-inducible gene in fibroblasts called TSG14. The C-terminal half of PTX3 aligns with CRP and SAP, but the N-terminal half is unique. PTX3 is induced by LPS, IL-1 and TNF-alpha, but not IL-6. During an acute phase response induced by LPS, PTX3 is expressed in many organs (heart, skeletal muscle). PTX3 expression may be indicative of its role in cardiovascular and inflammatory pathology.

Neuronal Pentraxins: A new family of putative integral membrane pentraxins or Neuronal pentraxins identified through interaction with a presynaptic snake venom toxin taipoxin. NPX1, NPX2 and NPXR (Neuronal Pentraxin Receptor), the three neuronal pentraxins represent a novel neuronal uptake pathway that may function during synapse formation and remodeling. The N-terminal half of neuronal pentraxins are 20-30% identical to previously identified pentraxins (CRP and SAP); the three neuronal pentraxins are 50% identical to each other and are significantly larger than the classical pentraxins (>50 versus 30kDa), suggesting that they may have additional novel functions.

NPX1 (Neuronal Pentraxin 1) a 432aa protein in mouse and rat, 430aa in human (chr 17q25) it mediate the uptake of degraded synaptic material, which could play an important role in synaptic remodeling, expressed in brain.

NPX2 (Neuronal Pentraxin 2), 429aa in mouse, 432 in rat and 431 in human (chr 7q21), mainly expressed in brain, pancreas, liver and testis. It is likely to play role in the modification of cellular properties that underlie long-term plasticity. NPX1, NPX2 has potential N-linked glycosylation sites.

NPXR1 (Neuronal Pentraxin Receptor 1) a 493aa protein in mouse, 494 in rat, and 499aa in human. The predominant form of NPXR contains a putative NH2 terminal transmembrane and all forms are glycosylated. It shows 49 and 48% homology with NPX1 and NPX2 respectively. NPXR message is expressed in neuronal regions that express NPX1 and NPX2.

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