Research in the Gelb lab is in the area of medicinal enzymology. Research is not based on a single approach, but rather a variety of modern experimental techniques are used to solve research problems. Most studies are carried out in the Gelb lab except for those that require certain specialized techniques such as X-ray crystallography and are therefore carried out in collaboration with other researchers. Because the areas of expertise of lab members are diverse, the lab provides an ideal forum for students and postdocs to learn new experimental approaches. This is accomplished not only by "hands-on" research experiences but also by the variety of scientific discussions that occur in various formats. The facilities in the newly constructed labs together with on-campus equipment centers provide all of the necessary tools for meeting research goals. The lab has received strong funding from the National Institutes of Health and a number of pharmaceutical companies which allows graduate students to devote most of their time to research.
A. Phospholipase A2, Eicosanoid Biosynthesis and Inflammation
Phospholipases A2 catalyze the hydrolysis of membrane phospholipids to produce a free fatty acid and a lysophospholipid. These enzymes liberate arachidonic acid from cellular phospholipids for the biosynthesis of eicosanoids (prostaglandins, leukotrienes, and others), and thus are of interest for understanding inflammation. The Gelb lab has been working on these enzymes since 1985 and is recognized as one of the top laboratories worldwide in this area. We are working on a collection of 14-kDa secreted mammalian phospholipases A2 (sPLA2) and 87-kDa cytosolic forms (cPLA2). Both types are involved in arachidonate release. The human and mouse genome contains genes coding for 10 sPLA2s, many of which were cloned by the Gelb and Lambeau (IPMC, Nice, France) labs. A subset of these are turning out to play important roles in important inflammatory diseases. For example, we have generated a mouse that is deficient in the group X sPLA2 and showed that this enzyme plays a critical role in airway inflammation related to asthma. We are working with Profs. W. Henderson and E. Chi in the Dept. of Medicine to further understand the role of PLA2s in asthma. Recent studies with Prof. D. Lee and J. Arm, Harvard Medical School, are aimed at unraveling the role of sPLA2s in arthritis. In addition to studying the role of PLA2s in disease models, we also study the role of these enzymes in eicosanoid generation in mammalian cells through the use state-of-the-art molecular and cellular biochemical techniques. We also use the structure of PLA2s to design small MW inhibitors.
The left image shows a thin section of an asthmatic mouse lung, and the right image is from a mouse that lacks group X sPLA2. Note that the airway lumen in the asthmatic lung is plugged with mucus, whereas the lumen in the knockout is clear.
X-ray structure of an sPLA2 containing a short chain phospholipid analog (green sticks) sitting in the active site slot.
The work is supported by the National Institutes of Health and Pfizer Corp.
B. Rational Design of Anti-Parasite Agents
Drugs are desperately needed for Malaria, African sleeping sickness and ChagasŐ diseases, which effect millions of people worldwide. Lack of financial interest for development of drugs for diseases that are endemic in developing countries has necessitated the development of these drugs in academic institutions.
i. Protein Farnesyltransferase Inhibitors as Anti-Malarials.
In the late 1980s, a collaboration between the Gelb and Glomset laboratories led to the discovery of protein prenylation (the attachment of farnesyl and geranylgeranyl groups to proteins in eukaryotic cells). Inhibitors of protein farnesyltransferase have been extensively developed in the pharmaceutical industry as anti-cancer agents. The Gelb laboratory discovered that these compounds display potent activity at killing the parasites that cause malaria and African sleeping sickness. We call this Ňpiggy-backÓ medicinal chemistry since we are making use of the pre-clinical and clinical data obtained in the pharmaceutical industry so that we can rapidly develop protein farnesyltransferase inhibitors as anti-parasite agents.
X-ray structure of a tetrahydroquinoline-based inhibitor (yellow) bound to the malarial protein farnesyltransferase.
ii. Lanosterol 14-Demethylase Inhibitors as Drugs for ChagasŐ Disease.
We discovered that tipifarnib, an anti-cancer, protein farnesyltransferase inhibitor, kills the parasite that causes ChagasŐ disease, Trypanosoma cruzi, by blocking lanosterol 14-demethylase. This enzyme is part of the ergosterol biosynthetic pathway in the parasite, and this sterol is a required component of the parasiteŐs membranes. We have taken a structure-based approach to modify tipifarnib so that it no longer binds to human protein farnesyltransferase and binds more tightly to the demethylase. Compounds in this series are the most potent anti-T. cruzi agents known to date and are now being transitioned into clinical trials.
The work is supported by the National Institutes of Health, Drugs for Neglected Diseases Initiative (DNDi) and Medicines for Malaria Venture (MMV).
C. Multiplex Clinical Enzymology and Newborn Screening
Lysosomal storage diseases are caused by deficiency in the activity of enzymes in the lysosome that are required for the degradation of cellular components. Many of these diseases have become treatable either by enzyme replacement therapy or by bone marrow transplantation. Halting the disease progression is most dramatic when treatment is started early in life. Thus, it makes sense to expand newborn screening programs to include lysosomal storage diseases. The Gelb laboratory is developing the use of tandem mass spectrometry for the direct assay of several lysosomal enzymes. The advantage of mass spectrometry is that many enzymes can be analyzed in a single infusion. The technique is exquisitely sensitive and rapid, and it is made quantitative by the use of internal standards.
The Gelb lab has developed a multiplex assay of 5 lysosomal enzymes using dried blood spots on newborn screening cards as the source of enzymes. The assay is now in use in New York state for screening for Krabbe disease and is being set up in Illinois, Austria and Taiwan for screening for Fabry, Gaucher, Krabbe, Niemann-Pick-A/B and Pompe diseases. Efforts are underway in the Gelb laboratory to develop assays for other lysosomal storage diseases and also for other genetic diseases.
Top panel shows our tandem mass spectrometry assay for Hurler syndrome. The bottom panel shows assay results using dried blood spots from Hurler patients, Hurler carriers and non-Hurler patients.
The work is supported by the National Institues of Health, Genzyme Corp. and BioMarin Corp.
Last update: March 14, 2008