Polycystin-1 Activation of c-Jun N-terminal Kinase and AP-1 Is Mediated by Heterotrimeric G Proteins

Abstract

Functional analysis of polycystin-1, the product of the gene most frequently mutated in autosomal dominant polycystic kidney disease, has revealed that this protein is involved in the regulation of diverse signaling pathways such as the activation of the transcription factor AP-1 and modulation of Wnt signaling. However, the initial steps involved in the activation of such cascades have remained unclear. We demonstrated previously that the C-terminal cytosolic tail of polycystin-1 binds and activates heterotrimeric G proteins in vitro. To test if polycystin-1 can activate cellular signaling cascades via heterotrimeric G protein subunits, polycystin-1 Cterminal tail-mediated c-Jun N-terminal kinase (JNK) and AP-1 activities were assayed in transiently transfected 293T cells in the presence of dominant-negative, G protein inhibiting constructs, and in the presence of cotransfected G␣ subunits. The results showed that polycystin-1-mediated JNK/AP-1 activation is mediated by G␣ and G␤␥ subunits. Polycystin-1-mediated AP-1 activity could be significantly augmented by cotransfected G␣ i , G␣ q , and G␣ 12/13 subunits, suggesting that polycystin-1 can couple with and activate several heterotrimeric G protein families.

Aberrant Polycystin-1 Expression Results in Modification of Activator Protein-1 Activity, whereas Wnt Signaling Remains Unaffected

“…We propose that polycystin-1 is capable of inducing at least c-Jun and ATF2 activity and that the gene transcriptional effect of this activation is tightly regulated and depends on variables such as cellular context and experimental conditions. The C-terminal 29-amino acid difference between our sequence and the construct used by Parnell et al (7) may contain a regulatory domain determining Jun-ATF or Jun-Fos activation. Divergent mechanisms of AP-1 activation have been reported to be a major regulatory mechanism to determine the cellular response upon a certain stimulus (reviewed in Refs.…”

“…The protein level of c-Fos was not affected by the mouse C-terminal polycystin-1 construct, and activation of Jun-Fos dependent luciferase reporters was not detected under our experimental conditions. Parnell et al (7) have recently reported activation of a Jun-Fosspecific luciferase reporter using a construct containing the C-terminal 222 amino acids of mouse polycystin-1. We propose that polycystin-1 is capable of inducing at least c-Jun and ATF2 activity and that the gene transcriptional effect of this activation is tightly regulated and depends on variables such as cellular context and experimental conditions.…”

“…Overexpression of the C-terminal region of polycystin-1 in human embryonic kidney 293T (HEK293T) cells has been shown to activate the Wnt signaling pathway (5) and the activator protein-1 (AP-1) transcription factor complex (6,7). Furthermore, overexpression of a full-length polycystin-1 construct has been reported to activate the Janus kinase and signal transducer and activator of transcription (JAK-STAT) signaling pathway (8).…”

A polycystin multiprotein complex constitutes a cholesterol-containing signalling microdomain in human kidney epithelia

“…Given the large size of native polycystin-1, we comparatively evaluated the gradient fractionation of a chimaeric, transmembrane form of the C-terminus of polycystin-1 that is known to be active in intracellular signalling [30][31][32]. The overexpressed C-terminus of polycystin-1 retained the ability to complex with flotillin-2 based on co-precipitation experiments ( Figure 4A).…”

Structural model of the TRPP2/PKD1 C-terminal coiled-coil complex produced by a combined computational and experimental approach

“…For example, PKD1 interacts with and activates heterotrimeric G i∕o proteins, potentially affecting diverse downstream signaling pathways (18)(19)(20)(21). On the other hand, TRPP2 interacts and forms functional heteromeric cation channels with other TRP channel subunits, including TRPC1 and TRPV4 (9,(22)(23)(24).…”