The neurochemical nature of PrPc-containing cells in the rat brain

Selective vulnerability to neurodegenerative disease: the curious case of Prion Protein

The mechanisms underlying the selective targeting of specific brain regions by different neurodegenerative diseases is one of the most intriguing mysteries in medicine. For example, it is known that Alzheimer’s disease primarily affects parts of the brain that play a role in memory, whereas Parkinson’s disease predominantly affects parts of the brain that are involved in body movement. However, the reasons that other brain regions remain unaffected in these diseases are unknown. A better understanding of the phenomenon of selective vulnerability is required for the development of targeted therapeutic approaches that specifically protect affected neurons, thereby altering the disease course and preventing its progression. Prion diseases are a fascinating group of neurodegenerative diseases because they exhibit a wide phenotypic spectrum caused by different sequence perturbations in a single protein. The possible ways that mutations affecting this protein can cause several distinct neurodegenerative diseases are explored in this Review to highlight the complexity underlying selective vulnerability. The premise of this article is that selective vulnerability is determined by the interaction of specific protein conformers and region-specific microenvironments harboring unique combinations of subcellular components such as metals, chaperones and protein translation machinery. Given the abundance of potential contributory factors in the neurodegenerative process, a better understanding of how these factors interact will provide invaluable insight into disease mechanisms to guide therapeutic discovery.

Upregulation in rat spinal cord microglia of the nonintegrin laminin receptor 37 kDa-LRP following activation by a traumatic lesion or peripheral injury

The molecular mechanisms triggering microglial activation after injury to the central nervous system, involving cell-extracellular matrix interactions and cytokine signaling, are not yet fully understood. Here, we report that resident microglia in spinal cord express low levels of the non-integrin laminin receptor precursor (LRP), also found on certain neurons and glial cells in the peripheral nervous system. 37LRP/p40 and its 67-kDa isoform laminin receptor (LR) were the first high-affinity laminin binding proteins identified. While the role of laminin receptor was later attributed to integrins, LRP/LR gained new interest as receptors for prions, and their interaction with laminin seems important for migration of metastatic cancer cells. Using immunohistochemistry and Western blotting, we demonstrate that traumatic spinal cord injury leads to a strong and rapid increase in LRP levels in relation to activated microglia/macrophages. Associated with laminin re-expression in the lesion epicenter, LRP-positive microglia/macrophages exhibit a rounded, ameboid-like shape characteristic of phagocytic cells, whereas in more distant loci they reveal a hypertrophied cell body and short ramifications. The same morphological difference is observed in vitro for purified microglia cultured with or without laminin. Strong, transient upregulation of LRP by activated spinal cord microglia is also induced by transection of the sciatic nerve that affects the spinal cord circuitry without blood-brain barrier dysruption. LRP expression is maximal by 1 week post-lesion, before becoming restricted to dorsal and ventral horns, sites of major structural reorganization. Our findings strongly suggest the involvement of LRP in lesion-induced activation and migration of microglia.