Evidence of STAT1 phosphorylation modulated by MAPKs, MEK1 and MSK1

Abstract

Phosphorylation at Ser727 in signal transducer and activator of transcription 1 (STAT1) is essential for its activation and signal transduction. However, the upstream kinases responsible for phosphorylating Ser727 are still elusive. Here, we provide evidence showing that UVA-induced mitogen-activated protein kinase (MAPK) signaling pathways lead to STAT1 Ser727 phosphorylation. Our experimental results show that UVA-induced Ser727 phosphorylation of STAT1 was, to different degrees, diminished by PD98059 and U0126, two specific inhibitors of MEKs, and SB202190 and PD169316, inhibitors of p38 kinase and c-Jun N-terminal kinases (JNKs), respectively. STAT1 phosphorylation was also blocked by a dominant negative mutant of p38beta kinase or JNK1, JNK1- or JNK2-deficiency, or an N-terminal or C-terminal kinase-dead mutant of mitogen- and stress-activated protein kinase 1 (MSK1), a downstream kinase closer to p38 kinase and extracellular signal-regulated kinases (ERKs). In vitro kinase assays using the combined STAT1 proteins as substrates from immunoprecipitation and glutathione S-transferase pull down show that active ERK1, JNK1, p38 kinase, MEK1 and MSK1 stimulated phosphorylation of STAT1 (Ser727) indirectly through an unidentified factor or a downstream kinase. Overall, our data indicate that phosphorylation of STAT1 at Ser727 occurs through diverse MAPK cascades including MEK1, ERKs, p38 kinase, JNKs and MSK1 in the cellular response to UVA.

HIV-1 gp120 induces cytokine expression, leukocyte adhesion, and transmigration across the blood–brain barrier: modulatory effects of STAT1 signaling

“…Phosphorylation of JAK1, JAK2, JAK3, or TYK2 was not detected in gp120-treated cells (data not shown). There is evidence that STAT1 and STAT3 can also be phosphorylated by serine threonine kinase, including mitogen activated protein kinase (MAPK) and MEK (Kovarik et al, 2001; Zhang et al, 2004). To investigate this possibility, we determined the effect of FLUD (a specific STAT1 inhibitor), PD98059 (a specific MEK inhibitor), SB202190 (a specific p38 MAPK inhibitor), and LY294002 (a specific PI3K inhibitor) on gp120-induced STAT1 activation.…”

“…We demonstrated that STAT1 and STAT3 are the STAT family members activated by gp120 proteins, which suggests that in gp120-induced BBB dysfunction, the STAT dimers that translocate to the nucleus consist of STAT1-STAT3 heterodimers. Upstream effectors of STATs include JAK and serine threonine kinase such as MEK and PI3K (Kovarik et al, 2001; Zhang et al, 2004). Other studies showed crosstalk between MAPK, PI3K, and protein kinase C (PKC) signaling pathways in gp120-induced toxicity of human umbilical vein endothelial cells (Langford et al, 2005).…”

Persistent and non-persistent changes in gene expression result from long-term estrogen exposure of MCF-7 breast cancer cells

“…The relative contributions of the AREG autocrine loop and the rapid signaling pathway mediated by plasma membrane ER␣ are currently unknown; however, both could contribute to ERK1/2-mediated signaling. ERK1/2 activation is associated with the regulation of gene expression [40], cancer-cell proliferation, and the phosphorylation of STAT1 [41][42][43], which involves the direct recruitment of STAT1 to the cytoplasmic C-tail of EGFR [44], and/or RAS-mediated MAP kinase activation [29]. Activated STAT1 is known to induce its own expression and that of other components of STAT signaling in a positive feedback loop [45].…”

“…Since E 2 is known to activate cellular signaling pathways, including those involving MAP kinase and AKT, and since STAT1 activation is thought to be regulated by activated MAPK signaling through ERK1/2 phosphorylation [29], we investigated the phosphorylation , and LTEE cells that were propagated in DC5 medium without added E2 for an additional 25 days (LTEE (-E2), grey columns) were cultured to confluence in 6-well plates. RNA was then isolated, and real-time PCR of AhR, CYP1B1, STAT1, ISG15, and AREG was performed; data are the means ± SE, n = 3.…”

IFN‐γ‐induced BACE1 expression is mediated by activation of JAK2 and ERK1/2 signaling pathways and direct binding of STAT1 to BACE1 promoter in astrocytes

“…5E). Activated IFN-g binding receptor in the plasma membrane after binding IFN-g activates JAK2, which phosphorylates the Tyr701 residue of STAT1 and ERK1/2 to phosphorylates the Ser727 residue of STAT1 (Huang et al, 2004;Lee et al, 2003;Song et al, 2002;Zhang et al, 2004). These phosphorylated STAT1 proteins translocate to the nucleus after forming homo-or hetero-dimmer then bind to the response element (TTCCTCTAA) within the BACE1 promoter region to modulate BACE1 gene transcription in astrocytes.…”