Polycystin-1 (PC1) mutations result in proliferative renal
cyst growth and progression to
renal failure in
autosomal dominant polycystic kidney disease (
ADPKD). The
transcription factor STAT3 (
signal transducer and activator of transcription 3) was shown to be activated in
cyst-lining cells in
ADPKD and PKD mouse models and may drive renal
cyst growth, but the mechanisms leading to persistent STAT3 activation are unknown. A proteolytic fragment of PC1 corresponding to the cytoplasmic tail, PC1-p30, is overexpressed in
ADPKD. Here, we show that PC1-p30 interacts with the nonreceptor
tyrosine kinase Src, resulting in Src-dependent activation of STAT3 by
tyrosine phosphorylation. The PC1-p30-mediated activation of Src/STAT3 was independent of JAK family
kinases and insensitive to the STAT3 inhibitor suppressor of
cytokine signaling 3. Signaling by the
EGF receptor (EGFR) or cAMP amplified the activation of Src/STAT3 by PC1-p30. Expression of PC1-p30 changed the cellular response to cAMP signaling. In the absence of PC1-p30, cAMP dampened EGFR- or IL-6-dependent activation of STAT3; in the presence of PC1-p30, cAMP amplified Src-dependent activation of STAT3. In the
polycystic kidney (PCK) rat model, activation of STAT3 in renal cystic cells depended on
vasopressin receptor 2 (V2R) signaling, which increased cAMP levels. Genetic inhibition of
vasopressin expression or treatment with a pharmacologic V2R inhibitor strongly suppressed STAT3 activation and reduced renal
cyst growth. These results suggest that PC1, via its cleaved cytoplasmic tail, integrates signaling inputs from EGFR and cAMP, resulting in Src-dependent activation of STAT3 and a proliferative response.