What we do

 

Our brain controls our lives and is the most complex organ of our body.  Some 20 -30 billion neurons maintain a synaptic network supported by an array of glial cells performing specific functions such as axonal sheathing (oligodendrocytes)(slide 1), homeostasis (astrocytes) and debris removal (microglia).  For over 40 years my lab has been focused on understanding the consequences of inherited mutations in the genes for proteins (enzymes) which make and break lipids.  Lipids account for 40% of the dry weight of grey matter and 60% of white matter and show enormous diversity.  Abnormalities in their synthesis, transport and breakdown result in the most intractable diseases of mankind from dementias, movement disorders, manic-depressive disorders and lysosomal storage diseases. Our approach has changed over the years to benefit from the data explosion resulting from advances in genomics, proteomics and lipidomics and the development of model systems to study diseases, from worms, flies and fish to mice. Despite these advances we are really only at the end of the beginning in our understanding and “there are things we don’t know that we don’t know” about the brain.

The main support for my lab is from NIH and we currently have funding through 2016 (NS36866-37 and HD09402) to support two major ventures:

Sphingolipids

1.            We study several models of human disease, growth and development with innovative technology (slides2,3, and 4) to better understand the role of glycolipids and sphingolipids in mental retardation, and to devise therapeutic approaches.  An example of this is our recent discovery that deletion of the smpd3 gene for membrane sphingomyelinase in mice reveals that depletion of the bioactive lipid ceramide affects brain growth and skeletal development through an increased S1P/ceramide ratio and dysregulation of Akt-phosphorylation, and hyaluronic acid synthase2. In contrast, deletion of the gene for lysosomal sphingomyelinase results in a bigger increase in  sphingomyelin accumulation, exploding neurons but little effect on skeletal development. Thus targets of the two functionally similar enzymes are therefore quite different. We use chromatography-mass-spectrometry-based technology coupled with genetic manipulation and use of fluorescent probes.

        Galenya is a drug which attacks T-cells and reduces relapses in multiple sclerosis (MS) but also accumuates in lysosomes and inhibits sphingomyeliase. It both mimics and competes with S1P (which inhibits histone deacetylases) and we can use proteomics to identify specific protein acylation patterns resulting from Galenya use which may suggest an additional benefit to MS patients. Our network of collaborators also enables us to study the role of brain sphingolipids in sleep disorders, alcohol abuse, multiple sclerosis and cancer. The goal is to come up with new drugs to help treat these diseases but first we have to figure out how to get them into the right cells (eg: neurons) in the brain.

2.       Our approach to this problem utilizes a small molecule “chaperone” to potentially help children with mis-sense mutations in genes encoding a lysosomal protein.  The single amino acid substitution often results in normal protein synthesis but eventual misfolding. (slide 5,  6 and 7) Because of this, the cell’s quality control mechanisms destroy up to 98% of the misfolded enzyme.  The remaining 2%, while misfolded, is still able to degrade some substrate, resulting in later onset of disease and providing a wider therapeutic window.  We are trying to design and target small peptides-chaperone complexes to the brain in order to protect the protein from degradation and deliver more enzyme.  Chaperone design is achieved by means of molecular modeling based on x-ray crystallography data combined with sophisticated peptide chemistry.  Chaperone targeting is achieved by conjugating the peptide to soluble nanoparticles (quantum dots) that can specifically target neurons of the CNS after crossing the blood brain barrier.