Bioimaging of Cortiosteroid Receptor Dynamics
Abstract: Adrenal corticosteroids (cortisol in humans or corticosterone in rodents) exert numerous effects on the central nervous system that regulates the stress response, mood, learning and memory, and various neuroendocrine functions. Corticosterone (CORT) actions in the brain are mediated via two receptor systems: the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). These receptors are mainly distributed in the cytoplasm in the absence of hormones and translocated into the nucleus following exposure to hormones to act as transcriptional factors. Thus the subcellular dynamics of both receptors remain important issues under active investigation. Given the differential action of MR and GR in the central nervous system, it is of great interest to clarify how these receptors traffic between cytoplasm and nucleus and how their interactions are regulated by hormones and/or other molecules to exert their transcriptional activity. In this chapter, we describe corticosteroid receptor dynamics in living cells focusing on 1) time-lapse imaging of green fluorescent protein (GFP)-labeled corticosteroid receptors; 2) intranuclear dynamics of GFP-labeled corticosteroid receptors using the fluorescence recovery after photobleaching (FRAP) technique and the fluorescence resonance energy transfer (FRET) technique. We discuss various factors affecting the dynamics of these receptors. Furthermore, we present the future directions of in vivo molecular imaging of corticosteroid receptors at the whole brain level.
Key words: GFP, real-time imaging, in vivo imaging, FRAP, FRET