Lysosome Biogenesis
Our major objective is to delineate the biogenesis of the lysosome. Currently we focus on mouse models (Beige, Pale Ear, Pearl) of human diseases (Chediak-Higashi and Hermansky-Pudlak) to define how membrane proteins are targeted to the lysosomes and how failure to target these proteins leads to disease. To date we we have identified 215 proteins of the rat liver lysosomal integral membrane protein and plan to extend this to the mouse membrane. We are developing new methods for organelle purification from mouse liver, and have in place methods for characterization of luminal, membrane-associated, and integral lysosomal membrane proteins by advanced proteomics (electrophoretic or chromatographic separations of proteins followed by time-of-flight mass spectrometric identification of peptide sequences ).

Glycoproteins in C. elegans
Using proteomics techniques, we have identified 130 N-linked glycoproteins during development in C. elegans.

Organelle Proteomics Core Technology
The objective is to establish the methodological approaches to organellar (mitochondria, peroxisomes) proteomics.

As Director of the Genetic-Metabolic laboratory in the Department of Paediatric Laboratory Medicine at the Hospital for Sick Children, I am responsible for the analysis of several thousand patient samples each year to assist in the diagnosis of amino acidurias, organic acidurias, lysosomal and a variety of other rare disorders. We perform the most comprehensive testing for inborn errors of metabolism in the Province, and probably in Canada.

H. Zhang, X. Fan, R. D. Bagshaw, Li Zhang, D. J. Mahuran, J. W. Callahan.  Lysosomal membranes from Beige mice contain higher than normal levels of ER protein.(2007)  J. Proteome Res.  6: 240-249.

X. Fan, H. Zhang, S. Zhang, R. D. Bagshaw, M. B. Tropak, J. W. Callahan, D. J. Mahuran. Identification of the gene encoding the enzyme deficient in MPS IIIC (Sanfilippo disease type C).(2006)  Am J Human Genetics 79: 738-744.

R. D. Bagshaw, D. J. Mahuran, J. W. Callahan. A proteomic analysis of lysosomal integral membrane proteins reveals the diverse composition of the organelle. (2005) Molec. Cell Prot. 4: 133-143 with Issue Cover.

R. D. Bagshaw, D. J. Mahuran, J. W. Callahan, J. S. Ballantyne. Sulfatide and Na+-K+ -ATPase: a salinity-sensitive relationship in the gill basolateral membrane of rainbow trout. (2004) J. Membrane Biol. 201: 77-84.

X. Fan, Y. She, R. D. Bagshaw, J.W. Callahan, H. Schachter, D. J. Mahuran.A method for proteomic analysis of membrane-bound N-glycosylated proteins. (2004) Analyt. Biochem. 332:178-186.

S. H. Pasternak, J.W. Callahan, D. J. Mahuran.The role of the endosomal/lysosomal system in beta-amyloid production and the pathophysiology of Alzheimer’s disease: re-examining the spatial paradox from a lysosomal perspective. (2004) J. Alzheimer’s Disease 6: 53-65.

S. Pasternak, R. D. Bagshaw, M. Guiral, S. Zhang, C. A. Ackerley, B. J. Pak, J. W. Callahan, D. J. Mahuran. Presenilin-1, Nicastrin, Amyloid Precursor Protein, and g-secretase activity are co-localized in the lysosomal membrane. (2003) J. Biol. Chem. 278: 26687-94.

R. Bagshaw, S. Pasternak, D. Mahuran, J.W.Callahan. Nicastrin is a resident lysosomal membrane protein. (2003) Biochem. Biophys. Res. Comm. 300: 615-618.

R. Bagshaw, S. Zhang, A. Hinek, M.-A. Skomorowski, D. Whelan, J.T.R. Clarke, J.W.Callahan. Novel mutations (Asn484Lys, Thr500Ala, Gly438Glu) in Morquio B Disease. (2002) Biochim. Biophys. Acta 1588: 247-253.