Activation of protein kinase A alters subnuclear distribution pattern of human steroidogenic factor 1 in living cells.
BACKGROUND
The aim of this study was to identify the subnuclear distribution pattern of human orphan nuclear receptor steroidogenic factor 1 (SF-1) in living cells with and without the activation of protein kinase A (PKA) signal pathway, and thus try to explain the unknown mechanism by which PKA potentiates SF-1 transactivation.


METHODS
Full-length cDNAs of wild type and a naturally occurring mutant (G35E) human SF-1 were cloned and fused with green fluorescent protein (GFP). Subcellular distribution pattern of human SF-1 in living cells, whose PKA signaling was either activated or not, was studied by laser confocal microscopy after the validity of the gene sequence was confirmed.


RESULTS
The transactivation ability of the GFP-SF-1 chimeric protein was highly conserved. Wild type human SF-1 diffused homogeneously within the nuclei of cells when PKA was not active, and converged to clear foci when PKA was activated. Mutant SF-1 diffused within the nuclei even in the presence of PKA activation, surprisingly aggregating as fluorescent dots inside the nucleoli, a phenomenon not altered by PKA.


CONCLUSIONS
Activation of PKA causes wild type, but not mutant SF-1 to alter its subnuclear distribution pattern to a transactivationally active form (foci formation). This finding may throw new light on the mechanism by which PKA activates the orphan nuclear receptor.
Liu
Wei
W
Department of Medicine and Endocrinology, Renji Hospital, Shanghai Second Medical University, Pudong, 210127, China. liuwei@renji.com
Fan
Wu-qiang
WQ
Yanase
Toshihiko
T
Saitoh
Masayuki
M
Wu
Yin
Y
D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000032:analysis*; D004789:Enzyme Activation; D005260:Female; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D006801:Humans; D018613:Microscopy, Confocal; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000032:analysis*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases