Shedding of the 67-kD laminin receptor by human cancer cells

Looking into laminin receptor: critical discussion regarding the non-integrin 37/67-kDa laminin receptor/RPSA protein

The 37/67-kDa laminin receptor (LAMR/RPSA) was originally identified as a 67-kDa binding protein for laminin, an extracellular matrix glycoprotein that provides cellular adhesion to the basement membrane. LAMR has evolutionary origins, however, as a 37-kDa RPS2 family ribosomal component. Expressed in all domains of life, RPS2 proteins have been shown to have remarkably diverse physiological roles that vary across species. Contributing to laminin binding, ribosome biogenesis, cytoskeletal organization, and nuclear functions, this protein governs critical cellular processes including growth, survival, migration, protein synthesis, development, and differentiation. Unsurprisingly given its purview, LAMR has been associated with metastatic cancer, neurodegenerative disease and developmental abnormalities. Functioning in a receptor capacity, this protein also confers susceptibility to bacterial and viral infection. LAMR is clearly a molecule of consequence in human disease, directly mediating pathological events that make it a prime target for therapeutic interventions. Despite decades of research, there are still a large number of open questions regarding the cellular biology of LAMR, the nature of its ability to bind laminin, the function of its intrinsically disordered C-terminal region and its conversion from 37 to 67 kDa. This review attempts to convey an in-depth description of the complexity surrounding this multifaceted protein across functional, structural and pathological aspects.

Structural and functional analysis of the ovine laminin receptor gene (RPSA): Possible involvement of the LRP/LR protein in scrapie response

Scrapie is a prion disease affecting sheep and goats. Susceptibility to this neurodegenerative disease shows polygenic variance. The involvement of the laminin receptor (LRP/LR) in the metabolism and propagation of prions has previously been demonstrated. In the present work, the ovine laminin receptor gene (RPSA) was isolated, characterized, and mapped to ovine chromosome OAR19q13. Real-time RT-PCR revealed a significant decrease in RPSA mRNA in cerebellum after scrapie infection. Conversely, no differences were detected in other brain regions such as diencephalon and medulla oblongata. Association analysis showed that a polymorphism reflecting the presence of a RPSA pseudogene was overrepresented in a group of sheep resistant to scrapie infection. No amino acid change in the LRP/LR protein was found in the 126 sheep analyzed. However, interesting amino acid positions (241, 272, and 290), which could participate in the species barrier to scrapie and maybe to other transmissible spongiform encephalopathies, were identified by comparing LRP/LR sequences from various mammals with variable levels of resistance to scrapie.