I am broadly interested in the quantitative
study of the properties of signal transduction
pathways. Significant properties of interest
include basic input-output relationships, threshold
values, sensitivity, robustness of signaling,
noise, isogenic cell-cell heterogeneity, and
the role of feedback and multiple pathway cross-talk.
I have chosen to understand the determinants
of these properties in a eukaryotic system with
well-defined genetics and experimentally amenable
biochemistry, that of glucose sensing and signaling
in the model eukaryote Saccharomyces cerevisiae.
Budding yeast respond to the presence of extracellular
and intracellular glucose by means of multiple
signal transduction pathways, and I am examining
the properties of two well-defined pathways
that result in regulation of transcriptional
output in response to glucose. The SNF3/RGT2
pathway mediates the activation of transcription
in response to low glucose concentrations, while
the SNF1/AMPK pathway results in the repression
of transcription in response to higher concentrations
of glucose. These two discrete pathways coordinately
control transcriptional response to glucose
at a large number of promoters.
My initial approaches employ cDNA microarrays
and fluorescent promoter reporters to assay
pathway transcriptional output as a function
of input concentration,both in a wild-type background
and in strains that lack various pathway components,
as well as in the presence of pharmacologic
effectors or inhibitors of signaling. Future
goals include development of single cell real-time
fluorescent reporters to assess activity of
multiple levels of the pathways, basic modeling
of pathway component interactions and input-output
relationships, and construction of simple synthetic
pathways employing well-characterized modular
signaling elements.
