RESUMEN
The cytokine-inducible src homology 2 (SH-2) proteins, CIS (cytokine inducible SH-2 domain protein) and SOCS3 (suppressor of cytokine signaling 3), are implicated in the negative regulation of prolactin (PRL) receptor-mediated activation of signal transducer and activator of transcription 5 (STAT5). We have studied the expression and function of CIS and SOCS3 proteins in the mouse mammary gland and in HC11 mammary epithelial cells. CIS and SOCS3 were differentially regulated: high expression levels of CIS mRNA were measured during the second half of pregnancy, whereas SOCS3 expression was high during the first 12 d post conceptum. SOCS3 levels increased, whereas CIS levels decreased, in the initial phase of involution. At the beginning of the lactation period both CIS and SOCS3 were high. PRL and epidermal growth factor (EGF) were able to induce CIS and SOCS3, whereas glucocorticoids inhibited their expression in mammary epithelial cells. The effect of EGF was much stronger on SOCS3 than on CIS. Ectopic expression of both SOCS3 and CIS inhibited STAT5 activation. Our data indicate that in the mammary gland CIS and SOCS3 are involved in regulating STAT5 signaling at three different instances: 1) SOCS3 serves as a mediator of the inhibitory EGF effect on PRL-induced STAT5 activation; 2) CIS and SOCS3 play a role as negative feedback inhibitors of PRL action; 3) Inhibition of CIS and SOCS3 expression by glucocorticoids contributes to the positive effect of glucocorticoids on PRL-induced STAT5 activation.
Asunto(s)
Células Epiteliales/metabolismo , Proteínas Inmediatas-Precoces/metabolismo , Glándulas Mamarias Animales/metabolismo , Proteínas de la Leche , Proteínas/metabolismo , Proteínas Represoras , Factores de Transcripción , Dominios Homologos src , Animales , Células COS , Células Cultivadas , Proteínas de Unión al ADN/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Femenino , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Glucocorticoides/farmacología , Proteínas Inmediatas-Precoces/genética , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/crecimiento & desarrollo , Ratones , Fosforilación , Prolactina/farmacología , Proteínas/genética , Receptores de Prolactina/genética , Receptores de Prolactina/metabolismo , Factor de Transcripción STAT5 , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas , Transactivadores/metabolismoRESUMEN
Genome wide gene expression analysis by cDNA microarrays is often limited by minute amounts of starting RNA. We therefore tested an optimized linear RNA amplification protocol using the RiboAmp amplification kit in the setting of cDNA microarrays. We isolated mRNA from a human kidney cell line (HK-2; ATCC) and from Universal Human Reference RNA (STR; Stratagene). After performing one and two rounds of linear RNA amplification, respectively, the amplified RNAs were co-hybridized to cDNA microarrays. Linearity and reproducibility of the individual experiments were then assessed by calculating the Pearson correlation. The intra-amplification consistency showed a correlation of 0.968 for the first round, 0.907 for the second round and 0.912 for two successive rounds of amplification. If the first round was compared to unamplified material, r was 0.925. The second round amplification yielded a correlation of 0.897 if compared to unamplified mRNA. Two rounds of amplification starting from 200 pg of mRNA compared to unamplified material resulted in a correlation of 0.868. These results indicate that linear amplification using RiboAmp kit yields amplified RNA with a high degree of linearity and reproducibility.