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Publication - Professor Andres Lopez Bernal

    Steroid receptor co-activator interacting protein (SIP) mediates EGF-stimulated expression of the prostaglandin synthase COX2 and prostaglandin release in human myometrium


    Hudson, CA, McArdle, CA & Bernal, AL, 2016, ‘Steroid receptor co-activator interacting protein (SIP) mediates EGF-stimulated expression of the prostaglandin synthase COX2 and prostaglandin release in human myometrium’. Molecular Human Reproduction, vol 22., pp. 512-525


    Study hypothesis
    Steroid receptor coactivator interacting protein (SIP/KANK2) is involved
    in regulating the expression of the prostaglandin
    (PG)-endoperoxide synthase 2 (PTGS2; also known
    as cyclo-oxygenase 2, COX2) and PG release in human myometrium.

    Study finding SIP is
    phosphorylated in myometrial cells in response to epidermal growth
    factor (EGF)-stimulation and is required for EGF-stimulated
    increases in COX2 expression, PGE2 and PGF release, and expression of interleukins (IL) 6 and IL8.

    What is known already
    Human parturition involves inflammatory and non-inflammatory pathways
    and requires activation of the intrauterine PG cascade.
    A key mediator of uterine PG production is the
    highly inducible enzyme COX2. Regulation of COX2 expression is complex,
    novel factors involved in its induction may play
    an important role during labour. The expression and function of SIP in
    tissues has never been investigated.

    Study design, samples/materials, methods
    Mass spectrometry was used to identify SIP from cultured primary
    myometrial cells, and its expression in fresh placenta,
    fetal membranes, decidua and myometrium from
    pregnant and non-pregnant women was determined by western blotting. SIP
    in myometrial cells was reduced using small
    interfering RNA (siRNA), and COX2 expression was stimulated with EGF. COX2, IL6 and IL8 mRNA and COX2 protein expression were measured using quantitative RT-PCR (RT-qPCR) and western blotting respectively, and
    release of PGE2 and PGF
    by enzyme immunoassay. The time course and dose response of SIP
    phosphorylation in response to EGF were determined, and phosphorylation
    was measured in the presence of the
    mitogen-activated protein kinase kinase 1(MEK1) inhibitor PD-184352.
    Fresh myometrial
    tissue was used to confirm effects of EGF and
    MEK1 inhibition on SIP phosphorylation and COX2 expression. A profile of
    factor (TF) activity after SIP knockdown was
    carried out using a commercially available array.

    Main results and the role of chance
    We have demonstrated expression of SIP in human myometrium.
    siRNA-mediated knockdown of SIP resulted in decreased EGF-stimulated
    COX2 protein expression (P<0.001), and decreased release of PGE2 (P<0.001) and PGF (P<0.01)
    . EGF stimulation resulted in rapid and transient phosphorylation of
    SIP, which was blocked by pharmacological inhibition
    of the MEK1/ERK (extracellular signal-regulated
    kinase) signalling pathway with PD-184352 (P<0.001). Moreover inhibition of ERK signalling significantly decreased EGF-stimulated COX2 expression (P<0.001).
    EGF phosphorylated SIP and increased COX2 expression in a
    MEK1/ERK-dependent manner in freshly isolated pregnant
    myometrium. Our data have uncovered a pathway
    mediating EGF-stimulated COX2 expression that is ERK and SIP dependent,
    a novel function for SIP in the pregnant uterus.
    Furthermore, EGF stimulated the expression of IL6 and IL8 mRNA in a SIP-dependent manner (both P<0.05), and SIP expression was positively associated with activation of serum response factor (SRF) and YY1 TF (P<0.001 and P<0.05, respectively), suggesting additional important roles for myometrial SIP.

    Limitations, reasons for caution While we describe a new role for myometrial SIP, we are yet to determine whether SIP phosphorylation is required for its
    effects on regulating COX2 expression and PG release. Our data are from in vitro studies using fresh tissue and cultured myometrial cells at passage 7 therefore may not fully reflect the conditions in vivo.

    Wider implications of the findings
    Our group has previously described increases in myometrial COX2
    expression with labour at term and preterm. EGF levels rise
    in the amniotic fluid near term suggesting it
    may participate in paracrine signalling events, altering gene expression
    the myometrium. Our novel data describe a role
    for SIP in regulating EGF-stimulated expression of myometrial COX2 and
    PG release.
    Moreover, our profile of SIP-dependent TF
    activation provides a platform for further investigations into
    additional roles
    for SIP in uterine function. These findings may
    facilitate the development of new, targeted drugs for the management of

    Large scale data: Not applicable.

    Study funding and competing interest(s) This work was supported by an Action Medical Research grant (SP4612). The authors have no competing interests to declare.

    Full details in the University publications repository