It is important to understand the dynamic organization of membrane-bound molecules in order to arrive at a comprehensive view of cellular signaling mediated by membrane-bound receptors.1 We addressed the organization and dynamics of the human serotonin1A receptor fused to enhanced yellow fluorescent protein expressed in CHO cells. Serotonin1A receptors are prototypical members of the G-protein coupled receptor superfamily and represent a prime target for therapeutic actions of several anxiolytic and antidepressant drugs.2 Our recent work using z-scan fluorescence correlation spectroscopy (zFCS) provides novel insight on the effects of cholesterol depletion and actin cytoskeleton destabilization on receptor confinement.3 Interestingly, results from FRAP measurements performed under conditions of mild cytoskeletal destabilization suggest that receptor signaling is correlated with receptor mobility.4 We recently proposed, utilizing homo-FRET in live cells, that the serotonin1A receptor is present as constitutive oligomers and implicated the presence of higher-order oligomers.5,6 Taken together, these results on the cellular organization and dynamics of the serotonin1A receptor provide useful insight in understanding the function of the receptor in healthy and diseased states.1. Saxena, R., and Chattopadhyay, A. (2011) J. Neurochem. 116: 726-733.2. Pucadyil, T.J., Kalipatnapu, S., and Chattopadhyay, A. (2005) Cell. Mol. Neurobiol. 25: 553-580.3. Ganguly, S., and Chattopadhyay, A. (2010) Biophys. J. 99: 1397-1407.4. Ganguly, S., Pucadyil, T.J., and Chattopadhyay, A. (2008) Biophys. J. 95: 451-463.5. Ganguly, S., Clayton, A.H., and Chattopadhyay, A. (2011) Biophys. J. 100: 361-368.6. Paila, Y.D., Kombrabail, M., Krishnamoorthy, G., and Chattopadhyay, A. (2011) J. Phys. Chem. B (in press).