Laminin Beta 2 (LAMb2) Recombinant Protein

Laminins, a family of extracellular matrix glycoproteins, are the major noncollagenous constituent of basement membranes. They have been implicated in a wide variety of biological processes including cell adhesion, differentiation, migration, signaling, neurite outgrowth and metastasis. Laminins, composed of 3 non identical chains: laminin alpha, beta and gamma (formerly A, B1, and B2, respectively), form a cruciform structure consisting of 3 short arms, each formed by a different chain, and a long arm composed of all 3 chains. Each laminin chain is a multidomain protein encoded by a distinct gene. Several isoforms of each chain have been described. Different alpha, beta and gamma chain isomers combine to give rise to different heterotrimeric laminin isoforms which are designated by Arabic numerals in the order of their discovery, i.e. alpha1beta1gamma1 heterotrimer is laminin 1. The biological functions of the different chains and trimer molecules are largely unknown, but some of the chains have been shown to differ with respect to their tissue distribution, presumably reflecting diverse functions in vivo. This gene encodes the beta chain isoform laminin, beta 2. The beta 2 chain contains the 7 structural domains typical of beta chains of laminin, including the short alpha region. However, unlike beta 1 chain, beta 2 has a more restricted tissue distribution. It is enriched in the basement membrane of muscles at the neuromuscular junctions, kidney glomerulus and vascular smooth muscle. Transgenic mice in which the beta 2 chain gene was inactivated by homologous recombination, showed defects in the maturation of neuromuscular junctions and impairment of glomerular filtration. Alternative splicing involving a non consensus 5' splice site (gc) in the 5' UTR of this gene has been reported. It was suggested that inefficient splicing of this first intron, which does not change the protein sequence, results in a greater abundance of the unspliced form of the transcript than the spliced form. The full-length nature of the spliced transcript is not known. [provided by RefSeq, Aug 2011]

LAMB2: Binding to cells via a high affinity receptor, laminin is thought to mediate the attachment, migration and organization of cells into tissues during embryonic development by interacting with other extracellular matrix components. Defects in LAMB2 are the cause of Pierson syndrome (PIERSS); also known as microcoria-congenital nephrotic syndrome. Pierson syndrome is characterized by nephrotic syndrome with neonatal onset, diffuse mesangial sclerosis and eye abnormalities with microcoria as the leading clinical feature. Death usually occurs within the first weeks of life. Disease severity depends on the mutation type: nontruncating LAMB2 mutations may display variable phenotypes ranging from a milder variant of Pierson syndrome to isolated congenital nephrotic syndrome. Defects in LAMB2 are the cause of nephrotic syndrome type 5 with or without ocular abnormalities (NPHS5). NPHS5 is a renal disease characterized clinically by proteinuria, hypoalbuminemia, hyperlipidemia and edema. Kidney biopsies show non-specific histologic changes such as focal segmental glomerulosclerosis and diffuse mesangial proliferation. Some affected individuals have an inherited steroid-resistant form and progress to end-stage renal failure. NPHS5 is characterized by very early onset of progressive renal failure. A subset of patients may develop mild ocular anomalies, such as myopia, nystagmus, and strabismus.

Protein type: Extracellular matrix; Secreted; Motility/polarity/chemotaxis; Secreted, signal peptide

Chromosomal Location of Human Ortholog: 3p21

Cellular Component: extracellular matrix; laminin-3 complex; extracellular region; basement membrane; synapse; basal lamina

Molecular Function: integrin binding; structural molecule activity

Biological Process: axon guidance; extracellular matrix organization and biogenesis; Schwann cell development; visual perception; retina development in camera-type eye; axon extension involved in regeneration; cell adhesion; astrocyte development; neuromuscular junction development

Disease: Nephrotic Syndrome, Type 5, With Or Without Ocular Abnormalities; Pierson Syndrome