Email: barteltd@stjohns.edu
Intracellular Signal Transduction
Our laboratory is investigating the mechanisms by which
cells initiate reactions that lead to a change in their functional
state. Many cell functions including cell division are known to
occur only following an increase in the concentration of
intracellular calcium ion (Ca2+), and yet the nature of Ca2+
signalling in most cell types remains poorly understood. With the
advent of targeted expression of aequorin, a Ca2+-indicator
protein, it is now possible to measure Ca2+ concentrations in
specific subcellular compartments in vivo in real time.
We have chosen to perform our research using the filamentous
fungus Aspergillus nidulans because it is a simple eukaryotic
organism which undergoes development and differentiation during its
life cycle. It has a well characterized genome, the sequence of
which has recently been completed. A. nidulans is amenable to
molecular genetic manipulation. Specific alterations in genes can
be made by transformation with plasmid DNA is integrated into the
genome by homologous recombination. We have constructed strains of
A. nidulans that express aequorin in the cytoplasm and in
mitochondria. We have been able to demonstrate that environmental
stimuli such as oxidative stress, osmotic shock and cold shock
cause increases in both cytoplasmic and mitochondrial calcium(1).
We are currently constructing strains of A. nidulans expressing
targeted aequorin-green fluorescent protein chimeras which should
allow the visualization of Ca2+ fluxes in organelles of living
cells.
Previously we have isolated and characterized a
calmodulin-dependent protein kinase from A. nidulans (ACMPK), and
shown that it is an homologue of a protein kinase in mammalian
brain that has been implicated in the molecular basis of memory(2).
Antibodies to ACMPK were prepared and used in the
immunolocalization of the enzyme (see below) as well as in the
development of a quantitative assay(3). We isolated the gene
encoding ACMPK by expression cloning and determined its sequence.
The gene encoding ACMPK is present in a single copy and is
essential for viability of the organism (4). Research on the
identification of endogenous substrates for ACMPK is continuing
with a view toward determining which cellular processes it
regulates and why it is essential for viability.
Recent Publications
Greene, V., H. Cao, H., F.A.X.Schanne, and D. C. Bartelt
(2002) Oxidative stress-induced calcium signalling in Aspergillus
nidulans. Cellular Signalling 14, xxx (in press).
Bartelt, D.C., S. Fidel, L.H. Farber, D.J. Wolff, and R.L.
Hammell (1988) Calmodulin-dependent multifunctional protein kinase
in Aspergillus nidulans. Proc. Nat. Acad. Sci. (USA) 85,
3279-3283.
Manolas, B.M. and D.C. Bartelt (1998) Quantitative Immuno-Slot
Blot Assay to measure ACMPK protein in cell extracts of Aspergillus
nidulans. BioTechniques 24, 228-232.
Kornstein, L.B., M.L. Gaiso, R.L. Hammell, and D.C. Bartelt
(1992) Cloniong and sequence determination of a cDNA encoding
Aspergillus nidulans calmodulin-dependent multifunctional protein
kinase. Gene 113, 75-82.