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

Huang L, Pike D, Sleat DE, Nanda V and Lobel P. (2014) Potential pitfalls and solutions for use of fluorescent fusion proteins to study the lysosome. PLoS ONE 9:e88893

Meng Y, Sohar I, Sleat DE, Richardson JR, Reuhl KR, Jenkins RB, Sarkar G and 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

Sleat DE, Wiseman JA, Sohar I, El-Banna M, Zheng H, Moore DF, Lobel P. (2012) Proteomic analysis of mouse models of Niemann-Pick C disease reveals alterations in the steady-state levels of lysosomal proteins within the brain. Proteomics 12:3499-509

Xu S, Wang L, El-Banna M, Sohar I, Sleat DE, and 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

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