Associate Professor
Department of Pharmacology and Molecular Sciences
School of Medicine

jzhang32@bs.jhmi.edu

307 Hunterian Building
725 N. Wolfe Street
Baltimore, MD 21205

Office: 410-502-0173
Lab: 410-614-2892

Spatiotemporal Regulation of Signal Transduction

We are interested in the spatiotemporal regulation of cell signaling, with a particular focus on important signaling molecules such as protein kinases and second messengers.

Recent years have seen tremendous progress in identification of signaling components constituting a network of pathways that control cellular processes. Less well developed is our understanding of how these components are precisely regulated to achieve signaling specificity within a living cell, which may be reacting to multiple inputs simultaneously. The key is believed to lie in the spatiotemporal information encoded in a particular cellular context. We are investigating the molecular basis and cellular consequences of such spatiotemporal regulation by combining biochemical and biophysical approaches, including live-cell fluorescence microscopy.

As important cellular regulators, protein kinases are often spatially compartmentalized in microdomains, and such compartmentation is widely conjectured to be a key determinant in the specificity of various signaling pathways. In order to achieve direct measurement of kinase activities, we developed a general strategy for monitoring protein phosphorylation in living cells based on fluorescence resonance energy transfer (FRET). We are currently applying several kinase reporters to investigate the spatiotemporal regulation or dysregulation of protein kinases (e.g. PKA, Akt) in cell migration, energy metabolism and cancer development. Quantitative measurement from live-cell fluorescence imaging is combined with mechanistic computational modeling for systems analyses of signaling networks regulated by kinases. Furthermore, in our efforts to “illuminate the kinome”, we will build our knowledge about this important family of signaling regulators by undertaking large-scale studies including proteome-wide identification of kinase substrates.

Another important class of cellular regulators is small molecule second messengers, which regulate various effectors including protein kinases. To decipher the cellular information encoded in the spatiotemporal dynamics of these second messengers, we set out to develop and apply biochemical and biophysical tools that allow us to monitor and perturb their dynamics with precise spatial and temporal control.

New technologies are also being developed in the lab, for example, for manipulating molecular force and perturbing biochemical activity in living systems. The goal is to enable native biochemistry and biophysics studies to address many outstanding questions about the properties and behaviors of biomolecules in their native biological context.

The application of these novel technologies for studying signaling molecules in living systems should provide a better understanding of the molecular changes that regulate the cells’ inner workings, adding time and space dimensions and dynamic information to the current map of signal transduction networks. It is our hope that these studies will eventually lead to development of more effective therapeutic treatments that target the defects arising from dysregulated kinases and second messengers.

Support from NIH Director's Pioneer Award, NIH-NIDDK, 3M, and FAMRI.

Selected Publications
Gao, X., and J. Zhang. (2008) Spatiotemporal analysis of differential Akt regulation in plasma membrane microdomains. Mol. Biol. Cell 19:4366-4373.

Newman, R.H., and J. Zhang. (2008) Visualization of phosphatase activity in living cells with a FRET-based calcineurin activity sensor. Mol. BioSys. 4:496-501.

Violin, J.D.*, L.M. DiPilato*, T.C. Elston*,  N. Yildrim†,  J. Zhang J†, and R.J. Lefkowitz†. (2008) ß2-adrenergic receptor signaling and desensitization elucidated by quantitative modeling of real-time cAMP dynamics. *Equal contribution. † Co-corresponding authors J. Biol. Chem. 283:2949-2961.

Allen, M.D., and J. Zhang. (2008) A tunable FRET circuit for engineering fluorescent biosensors. Angew. Chem. Int. Ed Engl. 47:500-502.

Ananthanarayanan, B., M. Fosbrink, M. Rahdar, and J. Zhang. (2007) Live-cell molecular analysis of Akt activation reveals roles for activation loop phosphorylation. J. Biol. Chem. 282:36634-36641.

Zhang, J., and M.D. Allen. (2007) FRET-based kinase biosensors – Illuminating the kinome. Mol. Biosyst. 3:759-765.

Allen, M.D., L.M. DiPilato, M. Rahdar, Y.R. Ren, C. Chong, J.O. Liu, and J. Zhang. (2006) Reading dynamic kinase activity in living cells for high-throughput screening. ACS Chem. Biol. 1:371-376.

Allen, M.D., and J. Zhang. (2006) Subcellular dynamics of PKA activity visualized by FRET-based reporters. Biochem. Biophys. Res. Commun. 348:716-721.

Ni, Q., D.V. Titov, and J. Zhang. (2006) Analyzing protein kinase dynamics in living cells with FRET reporters. Methods 40:279-286.

Ananthanarayanan, B., Q. Ni, and J. Zhang. (2005) Signal propagation from membrane messengers to nuclear effectors revealed by reporters of phosphoinositide dynamics and Akt activity. Proc. Natl. Acad. Sci. USA 102:15081-15086.

DiPilato, L.M., X. Cheng, and J. Zhang. (2004) Fluorescent indicators of cAMP and Epac activation reveal differential dynamics of cAMP signaling within discrete subcellular compartments. Proc. Natl. Acad. Sci. USA 101:16513-16518.