Secretion of whey acidic protein and cystatin is down regulated at mid-lactation in the red kangaroo (Macropus rufus)

et al. 2004

Abstract. Although the biological role for whey acidic protein (WAP) in milk has been suggested, its true function is not known. This paper describes evidence for WAP function in the cell-cycle progression of EpH4/K6 (EpH4), mammary epithelial cells in vitro. The forced expression of exogenous WAP significantly impaired the proliferation of EpH4 cells, whereas it did not affect that of . Recently, it has also isolated from the milk of pigs [5,6], and three marsupial species, tamer wallaby [7], red kangaroo [8], and brushtail possum [9]. Expression of the WAP gene is regulated by lactogenic hormones, and the level of mo use WAP m RN A in the m am m ary gla nds incr eases t hous ands -fo ld between non-lactation and mid-lactation [10]. WAP proteins have a signal peptide [11] and two domain structures that are identified at the fourdisulfide core (4-DSC) domain, which is composed o f ei g h t c y s t ei n e r es id ue s i n a c o ns er v ed arrangement [12]. The 4-DSC domain arrangement is not exclusive to the WAP family, and a number of other proteins containing 4-DSC domains have been identified as protease inhibitors [11,[13][14][15][16], comprising either single or multiple copies of the 4-DSC domain. Generally, these proteins are secreted and may function as protease inhibitors [17,18]. Thus, based on the limited sequence identity with a known protease inhibitor, it has been postulated that WAP may be a secreting protease inhibitor [18,19], and its biological function has been suggested.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Inhibitory Function of Whey Acidic Protein in the Cell-Cycle Progression of Mouse Mammary Epithelial Cells (EpH4/K6 Cells)

Ikeda

et al. 2004

“…hey acidic protein (WAP) has been identified in the milk of a wide range of laboratory animals rodents [1,2], as well as in camels [3], rabbits [4], pigs [5], and three marsupial species, the tammar wallaby [6], brushtail possum [7], the red kangaroo [8]. In mice and rabbits, the expression of the WAP gene occurs in mammary epithelial cells during late pregnancy and throughout lactation, and is regulated by a variety of lactogenic hormones, including insulin, glucocorticoid, and prolactin [9][10][11][12][13][14].…”

mentioning

confidence: 99%

Analysis of the Promoter of Mutated Human Whey Acidic Protein (WAP) Gene

Seki

et al. 2006

Abstract. Although whey acidic protein (WAP) has been identified in the milk of a range of species, it has been predicted that WAP is not secreted into human milk as a result of critical point mutations within the coding region. In the present study, we first investigated computationally the promoter region of mutated human WAP genes by comparing with those of other known WAP genes. Computational database analyses showed that the human WAP promoter region was highly conserved, as in other species with milk WAP. Next, we evaluated the activity of the human WAP promoter (2.6 kb) using a reporter gene assay. MCF-7 cells were stably transfected with the hWAP/ hGH (human growth hormone) fusion gene, cultured on Matrigel, and treated with lactogenic hormones. Radioimmunoassay detected hGH in the culture medium, indicating that the human WAP promoter was responsible for the lactogenic hormones. The human WAP promoter was significantly more active in MCF-7 cells than the mouse WAP promoter (2.4 kb). The present results provide us with important information on the molecular evolution of milk protein genes.

“…β-casein is expressed during early pregnancy, while α-lactalbumin and whey acidic protein (WAP) are expressed around Days 13 and 14 of pregnancy, and these expressions are characterized by a terminal differentiation of the mammary secretory phenotype. WAP is a major whey protein found in the milk of rodents [4][5][6][7][8], as well as in rabbit [9], camel [10], swine [11,12], wallaby [13], and red kangaroo milk [14]. WAP proteins have a signal peptide and two domain structures that can be identified at the fourdisulfide core (4-DSC) [15].…”

mentioning

confidence: 99%

Aberrant Development of Mammary Glands, but Precocious Expression of .BETA.-casein in Transgenic Females Ubiquitously Expressing Whey Acidic Protein Transgene

Oosawa

et al. 2005

Abstract. It has been suggested that whey acidic protein (WAP) may function as a protease inhibitor. However, the actual function of WAP remains obscure. We investigated the histological development of the mammary glands of transgenic mice ubiquitously expressing WAP and CAG/WAP transgene. Ubiquitous expression of WAP induced aberrant development of the lobular alveoli of the mammary glands: mammary alveoli that were either aberrantly large or small in size increased in number in the developing mammary glands of these transgenic females during pregnancy and lactation. The expression of β-casein was precociously induced in the mammary glands of the transgenic females during early pregnancy and accompanying this was a histological observation that abnormally developed lobular alveoli filled with milk proteins appeared in the mammary glands of transgenic females during early pregnancy. However, during lactation, the development of mammary glands was impaired in transgenic females. To investigate the possible paracrine action of WAP associated with mammary gland aberration, we transplanted the mammary tissue of CAG/EGFP transgenic females into the fat pad of virgin CAG/WAP transgenic females and initiated pregnancy by mating. The development of mammary tissue transplanted to the recipient was histologically examined on day 3 of lactation. The results revealed that the development of grafted mammary tissues was impaired in a manner similar to that of the mammary glands of CAG/WAP transgenic females, indicating that the inhibitory effect of WAP acts via a paracrine mechanism. In vitro experiments using HC11 cells with forced expression of exogenous WAP demonstrated the inhibitory function of WAP on proliferation of mammary epithelial cells.Key words: β-casein, CAG/WAP, EGFP, HC11, Tissue graft (J. Reprod. Dev. 51: [579][580][581][582][583][584][585][586][587][588][589][590][591][592] 2005) evelopment of the mammary gland is achieved under the control of various hormones, including estrogen, progesterone, and prolactin [ 1 , 2 ] , a n d d r a m a t i c d e v e l o p m e n t a n d differentiation of the gland takes place during pregnancy and lactation. Between days 8 and 10 of pregnancy, the alveolar lobes in the mammary alveoli begin to increase in size. A rapid increase in the number and size of the alveoli occurs during the second half of pregnancy, resulting in the development of fully functional mammary glands with secretory lobular alveolar structures [3]. The synthesis of milk proteins increases dramatically during pregnancy and follows a characteristic time course; there is known to be variation in the precise onset of the expression of individual milk protein