title: Activation of signal transducer and activator of transcription 5 (STAT5) is linked to β1-integrin protein abundance in unilaterally milked bovine mammary glands.
abstract: Prolactin (PRL) is important in the regulation of milk synthesis in mammary epithelial cells (MEC). In cattle, circulating levels of PRL are not limiting, suggesting the possible involvement of other factors that may control the response to PRL at the cellular level. The effects of milking frequency (MF) on milk synthesis are controlled locally within mammary glands and involve PRL signaling. To further investigate this relationship between MF and PRL signaling, udder halves of 17 dairy cows were milked either 4 times a day (4×) or once a day (1×) for 14 d in early lactation. Mammary biopsies were obtained 3 to 5h following milking from both udder halves of 10 cows, and changes in PRL and associated pathways were measured. The abundance of STAT5A mRNA was higher after 4× milking, whereas that of the PRL receptor (PRLR) and STAT3 were lower relative to that after 1× milking. In 4× mammary tissues, the protein levels of STAT5, activated STAT5, and β1-integrin were higher, whereas the those of the long isoform of PRL receptor and activated STAT3 were lower than 1× tissues. The activation of STAT5 correlated strongly with major milk protein mRNA abundance (r=0.86 to 0.94) and β1-integrin protein levels (r=0.91). These results confirm that major milk protein gene expression is associated with STAT5 activation and suggests that the STAT5 and β1-integrin signaling pathways are linked. Modulation of β1-integrin abundance in response to changes in MF may be a mechanism that controls the MEC ability to respond to PRL and therefore its secretory activity.
authors.affiliation: AgResearch Ltd., Ruakura Research Centre, P.B. 3123, Hamilton 3240, New Zealand; Institute of Agriculture and Environment, College of Sciences, Massey University, P.B. 11222, Palmerston North 4442, New Zealand. Electronic address: regan.murney@agresearch.co.nz.
authors.forename: R
authors.initials: R
authors.lastname: Murney
authors.affiliation: SciLactis Ltd., Waikato Innovation Park, Hamilton 3240, New Zealand.
authors.forename: K
authors.initials: K
authors.lastname: Stelwagen
authors.affiliation: AgResearch Ltd., Ruakura Research Centre, P.B. 3123, Hamilton 3240, New Zealand.
authors.forename: T T
authors.initials: TT
authors.lastname: Wheeler
authors.affiliation: Institute of Agriculture and Environment, College of Sciences, Massey University, P.B. 11222, Palmerston North 4442, New Zealand.
authors.forename: J K
authors.initials: JK
authors.lastname: Margerison
authors.affiliation: AgResearch Ltd., Ruakura Research Centre, P.B. 3123, Hamilton 3240, New Zealand.
authors.forename: K
authors.initials: K
authors.lastname: Singh
mesh_terms: D000818:Animals; D002417:Cattle; D003612:Dairying / Q000379:methods*; D004847:Epithelial Cells; D005260:Female; D015870:Gene Expression; D006801:Humans; D019012:Integrin beta1 / Q000032:analysis / Q000378:metabolism*; D007774:Lactation / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000737:chemistry / Q000378:metabolism*; D008892:Milk; D008894:Milk Proteins / Q000235:genetics; D011388:Prolactin / Q000097:blood; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D019012:Integrin beta1; D008894:Milk Proteins; D012333:RNA, Messenger; D050799:STAT5 Transcription Factor; D011388:Prolactin
keywords: cell signaling; mammary; milk synthesis; milking frequency