Department of Biochemistry and Molecular Biology
RBHS, Robert Wood Johnson Medical School

Cancer Institute of New Jersey

Ph.D., 1986, Columbia University
Telephone: (848) 445-9831
Fax: (732) 235-4466

Lysosomal proteomics, diseases, and potential therapeutics

Our laboratory has pioneered proteomic methods for disease discovery that evolved from our basic research on lysosomal enzyme targeting. Lysosomes are membrane-bound, acidic organelles that are found in all eukaryotic cells. They contain a variety of different proteases, glycosidases, lipases, phosphatases, nucleases and other hydrolytic enzymes, most of which are delivered to the lysosome by the mannose 6-phosphate targeting system. In this pathway, lysosomal enzymes are recognized as different from other glycoproteins and are selectively phosphorylated on mannose residues. The mannose 6-phosphate serves as a recognition marker that allows the enzymes to bind mannose 6-phosphate receptors which ferry the lysosomal enzymes to the lysosome. In the lysosome, the enzymes function in concert to break down complex biological macromolecules into simple components. The importance of these enzymes is underscored by over forty different lysosomal storage disorders (e.g., Tay Sach's disease) where loss of a single lysosomal enzyme leads to severe health problems including neurodegeneration, progressive mental retardation and early death.

We have two basic approaches for disease discovery. In a “disease to protein” approach, we use proteomic methods to compare to complement of lysosomal proteins in control and disease specimens. If the disease specimen lacks a given lysosomal protein, this provides a clue for further genetic studies to determine if there are underlying mutations in the corresponding gene. In a “protein to disease” approach, we identify new lysosomal proteins and use their known or predicted properties to associate them with diseases of unknown etiology. Using such approaches we have identified the gene defect in several lysosomal storage disorders, most notably late infantile neuronal ceroid lipofuscinosis (LINCL) and Niemann Pick Type C2 disease.

We and our collaborators extend this discovery research in several directions. For newly solved disease, we develop biochemical and genetic tests for diagnosis and carrier screening. We also generate mouse models to investigate disease pathophysiology and to aid in the development of potential therapeutics. Another focus is to investigate the structural, biochemical, and functional properties of lysosomal proteins of interest, and to use this information to develop protein-based therapeutics. This multi-faceted approach continues to provide new insights and advances in lysosome biology and medicine.

Figure 1. Structural basis of pH-dependent autoproteolytic maturation of tripeptidly-peptidase I, the protein deficient in LINCL. Image depicts cleavage sites (diamonds, 1-3) and positions of ionizable residues (spheres 1-9) at the interdomain interface. The pro-TPP1 backbone is shown with the catalytic domain in orange, the prodomain in cyan, and the propiece linker in magenta. Active site residues (Ser475, Glu272, Asp276, and Asp360) are depicted in stick mode. Guhaniyogi et al, 2009, JBC.

Selected Publications

Wiseman JA, Meng Y, Nemtsova Y, Matteson PG, Millonig JH, Moore DF, Sleat DE, and Lobel, P. (2017) Chronic enzyme replacement to the brain of a late infantile neuronal ceroid lipofuscinosis mouse has differential effects on phenotypes of disease. Mol Ther Methods Clin Dev 4:204-212

Jadot M, Boonen M, Thirion J, Wang N, Xing J, Zhao C, Tannous A, Qian M, Zheng H, Everett JK, Moore DF, Sleat DE, Lobel P. (2017) Accounting for protein subcellular localization: A compartmental map of the rat liver proteome. Mol Cell Proteomics 16:194-212

Meng Y, Sohar I, Sleat DE, Richardson JR, Reuhl KR, Jenkins RB, Sarkar G, Lobel P. (2014) Effective intravenous therapy for neurodegenerative disease with a therapeutic enzyme and a peptide that mediates delivery to the brain. Mol Ther 22:547-53

Sleat DE, Sun P, Wiseman JA, Huang L, El-Banna M, Zheng H, Moore DF, Lobel P. (2013) Extending the mannose 6-phosphate glycoproteome by high resolution/accuracy mass spectrometry analysis of control and acid phosphatase 5-deficient mice. Mol Cell Proteomics 12:1806-17

Xu S, Wang L, El-Banna M, Sohar I, Sleat DE, Lobel P. (2011) Large-volume intrathecal enzyme delivery increases survival of a mouse model of late infantile neuronal ceroid lipofuscinosis. Mol Ther 19:1842-8

Guhaniyogi J, Sohar I, Das K, Stock AM, Lobel P. (2009) Crystal structure and autoactivation pathway of the precursor form of human tripeptidyl-peptidase 1, the enzyme deficient in late infantile ceroid lipofuscinosis. J Biol Chem 284:3985-97

Sun P, Sleat DE, Lecocq M, Hayman AR, Jadot M, Lobel P. (2008) Acid phosphatase 5 is responsible for removing the mannose 6-phosphate recognition marker from lysosomal proteins. Proc Natl Acad Sci USA 105:16590-5

Sleat DE, Wiseman JA, El-Banna M, Price SM, Verot L, Shen MM, Tint GS, Vanier MT, Walkley SU, Lobel P. (2004) Genetic evidence for nonredundant functional cooperativity between NPC1 and NPC2 in lipid transport. Proc Natl Acad Sci USA 101:5886-91

Sleat DE, Wiseman JA, El-Banna M, Kim KH, Mao Q, Price S, Macauley SL, Sidman RL, Shen MM, Zhao Q, Passini MA, Davidson BL, Stewart GR, Lobel P. (2004) A mouse model of classical late-infantile neuronal ceroid lipofuscinosis based on targeted disruption of the CLN2 gene results in a loss of tripeptidyl-peptidase I activity and progressive neurodegeneration. J Neurosci 24:9117-26

Tyynela J, Sohar I, Sleat DE, Gin RM, Donnelly RJ, Baumann M, Haltia M, Lobel P. (2001) Congenital ovine neuronal ceroid lipofuscinosis--a cathepsin D deficiency with increased levels of the inactive enzyme. Eur J Paediatr Neurol 5 Suppl A:43-5

Naureckiene S, Sleat DE, Lackland H, Fensom A, Vanier MT, Wattiaux R, Jadot M, Lobel P. (2000) Identification of HE1 as the second gene of Niemann-Pick C disease. Science 290:2298-301

Sleat DE, Donnelly RJ, Lackland H, Liu CG, Sohar I, Pullarkat RK, Lobel P. (1997) Association of mutations in a lysosomal protein with classical late-infantile neuronal ceroid lipofuscinosis. Science 277:1802-5