Head of Lab: Paul Mathews, Ph.D.

Mathews’ Lab Research Interests:

Our laboratory studies the cell biology of Alzheimer’s disease, in vitro using cultured cells and in vivo with transgenic mouse models of Alzheimer’s disease pathology. The group has a strong background in membrane protein trafficking, so our interests often gravitate toward understanding how alterations in vesicle trafficking or the movement of specific membrane proteins and their ligands through the secretory and endosomal pathways impact the progression of the disease.

Fig. 1: Ab is generated from APP by sequential b- and g-cleavage. a-cleavage, an alternative proteolytic event, occurs within the Ab peptide sequence and as such prevents Ab generation. The Mathews’ laboratory continues to develop antibody-based assays that can be used to detect and quantify various of the metabolites generated from APP, including Ab, APP itself, and the C-terminal proteolytic fragments.

Amyloid Precursor Protein Trafficking
Currently, we are focused on expanding our understanding of the interplay between the intracellular trafficking of Amyloid Precursor Protein (APP) and its proteolytic fate. We have recently shown that the b-cleavage of APP can be promoted by multiple mechanisms that impact the movement of APP through endocytic compartments. Given that b-cleavage is the initial and rate-limiting proteolytic step in Ab generation, understanding how the subcellular compartmentalization of APP can be altered may be key in the therapeutic manipulation of APP proteolysis and the development of anti-Ab interventions. For instance, we have recently shown that the activity of intracellular, calcium-activated proteases known as calpains can modulate the subcellular distribution of APP. We are now examining the interrelationship between neuronal calpain activity and Ab production and deposition in transgenic mice. We are also investigating the role of the presenilin protein complex in the endosomal proteolysis of APP, including g-cleavage favoring generation of 40- or 42-residue Ab.

Endosomal System Upregulation in AD
We also know that the endosomal system in neurons is upregulated very early in the most common, sporadic form of Alzheimer’s disease. We are modeling this by overexpressing important trafficking and regulatory proteins of the endosomal system, such as the mannose 6-phosphate receptors, which mediate the delivery of many lysosomal hydrolases, and various rab GTPases, which regulate vesicular transport and fusion events. Using these models, we are examining changes in APP metabolism, asking whether Ab generation or clearance is affected, and determining the impact of endosomal pathway upregulation on other proteins that may play a prominent role in neuronal degeneration.

ELISA Development
Additionally, the group has developed a number of antibody-based assays that allow us to dissect APP metabolism in detail. We have developed highly sensitive sandwich ELISAs that detect various Ab species, derived from either human and rodent APP. These ELISAs have been critical in the biochemical characterization of a number of transgenic and knock-out mouse models relevant to human Alzheimer’s disease. We have created sandwich ELISAs that allow us to detect many of the cell-associated metabolites of APP, including the b-cleaved C-terminal fragment of APP (bCTF). We are currently adapting some of these ELISA techniques for use in high-throughput screening of Ab inhibitors using living cells.