Super-resolution imaging of STAT3 cellular clustering during nuclear transport

Abstract

Signal transducer and activator of transcription 3 (STAT3) mediates signals from the plasma membrane to the nucleus, and participates in gene expression in response to cytokines and growth factors. STAT3 translocation to the cell nucleus and subsequent recycling into the cytoplasm is the critical step for multiple functions. However, the distribution and molecular composition of STAT3 during the nuclear transport upon activation by different stimuli remains largely elusive. By direct stochastic optical reconstruction microscopy (dSTORM), we visualized the nucleocytoplasmic distribution of STAT3 in HeLa cells following different stimuli. Our work reveals that STAT3 is preclustered in the cytoplasm before activation, and that interleukin-6 promotes the formation of more and larger clusters. Further analysis indicates that STAT3 clusters vary with the nuclear translocation of STAT3. Moreover, dual-color dSTORM imaging shows the colocalization of STAT3 and STAT1 clusters, and suggests that the ratios of their colocalization are associated with STAT functions.