Diana Bartelt, Ph.D.

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.