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.
Take a tour of the Gelb
laboratories.
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 ChagasÕ 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 Òpiggy-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 ChagasÕ Disease.
We discovered that
tipifarnib, an anti-cancer, protein farnesyltransferase inhibitor, kills the
parasite that causes ChagasÕ 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 parasiteÕs 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