Review: Lutheran/B-CAM: A Laminin Receptor on Red Blood Cells and in Various Tissues

Abstract

The Lutheran blood group glycoprotein (Lu), also known as basal cell adhesion molecule (B-CAM), is a transmembrane receptor with five immunoglobulin-like domains in its extracellular region; it is therefore classified as a member of the immunoglobulin (Ig) gene family. Lu/B-CAM is observed not only on red blood cells, but also on a subset of muscle and epithelial cells in various tissues. Recently, several groups have reported that Lu/B-CAM is a novel receptor for laminin a5. The laminin a5 chain is a component of the laminin-511 (alpha 5 beta 1 gamma 1), -521 (alpha 5 beta 2 gamma 1), and -523 (alpha 5 beta 2 gamma 3) heterotrimers and is expressed throughout the mammalian body. We also have shown that Lu/B-CAM is co-localized with laminin alpha 5 in various tissues. Although the biological role of Lu/B-CAM remains unclear, the specific binding of Lu/B-CAM to laminin alpha 5 suggests that it plays an important role in developmental and physiological processes. It also is necessary to investigate further the interaction between Lu/B-CAM and laminin a5 in pathological processes, including sickle cell disease and cancer.

Blood vessels of human islets of Langerhans are surrounded by a double basement membrane

“…Since on the basis of differential splicing, two distinct isoforms of Lu/B-CAM are known to exist [30], we used PCR with specific primers to identify these two mRNA variants in human islets. The 5′-primer is common to both mRNA forms, but the 3′-primers are designed specifically to distinguish the 3′-end of the Lu mRNA coding region from the mRNA of B-CAM not containing this region that codes the cytoplasmic src-homology 3 domain binding area and Ser/Thr phosphorylation sites.…”

“…We also studied the presence of the putative integrin and non-integrin receptors for Lm-511/-521, which comprise integrins α 2 β 1 , α 3 β 1 , α 6 β 1 and α 6 β 4 , α v β 3 , dystroglycan protein complex and the Lu blood group antigen, as reviewed [10,30]. Our results show that in adult human islet tissue immunoreactivities for both integrin β 1 and α 3 are diffusely distributed on endocrine cells without any apparent polarisation towards BM [37] and that immunoreactivities for dystroglycan showed a typical punctate pattern.…”

“…Remarkably, Lu was very prominent in polarised distribution in the most peripherally located islet cells, strongly suggesting that it is the major Lm-511/-521 binding receptor of endocrine cells. While only little is known about the specific functions of Lu [30], it has been shown that mesangial cells organise the glomerular capillaries via α5-Lm-Lu-integrin interactions [25], suggesting that such interactions may also function at the endocrineexocrine interface in the human pancreas. Direct evidence for the role of Lu in the anchorage of endocrine cells to Lm-511 has come from cell adhesion studies.…”

Novel role for the Lu/BCAM–spectrin interaction in actin cytoskeleton reorganization

“…Copying is not permitted, except with prior permission and as allowed by law. [8]. Indeed, Lu/BCAM expression was dramatically reduced in various tissues of mouse embryos lacking laminin D5 chain, while it was significantly increased in the heart of transgenic mice overexpressing this chain [29,30].…”

Active Peptide-Conjugated Chitosan Matrices as an Artificial Basement Membrane

“…Laminins also bind to syndecans, membrane-associated heparan sulfate proteoglycan, via their heparan sulfate chains [22][23][24][25][26]. Additionally, α-dystroglycan binding to the laminin α1 and α2 chains and the Lutheran/basal cell adhesion molecule (Lu/BCAM) binding to the laminin α5 chain are identified as laminin isoform-specific receptors [12,[27][28][29]. These multiple and diverse cell surface receptors bind to the laminins in different ways depending on the laminin isoforms.…”