PARENT SESSION
BIOLOGY OF PREGNANCY AND IMMUNE FUNCTION
Harborside C
7:30 AM-10:00 AM

(321) A STRATEGY FOR IDENTIFYING BOVINE PROLACTIN FAMILY INTERACTIONS WITH TARGET TISSUES.

Takahashi, Toru¹, Lu, Lu¹, Ain, Rupasri¹, Alt, Adam¹, Li, Chunbin¹, Dai, Guoli¹, Hashizume, Kazuyoshi², Schuler, Linda³, Soares, Michael¹, ¹ Department of Molecular and Integrative Physiology, Kansas City, KS² Laboratory of Reproductive Biology and Technology, Ibaraki, JP³ Department of Comparative Biosciences, Madison, WI

ABSTRACT- The bovine prolactin (PRL) family consists of at least eight genes bearing structural relationships with PRL. These genes encode for hormones/cytokines expressed either by the anterior pituitary (PRL) or the placenta (remaining seven members). The hormones/cytokines are hypothesized to coordinate maternal and fetal adaptations to pregnancy. Target tissues and physiological roles for many members of the bovine PRL family are yet to be determined. In this investigation, we have evaluated the use of an alkaline phosphatase (AP) tagging system for monitoring the behavior of three members of the bovine PRL family, placental lactogen (PL), PRL-related protein-I (PRP-I), and PRP-VI. Probes were generated consisting of a fusion protein of human placental AP and either PL, PRP-I, or PRP-VI. The AP fusion proteins were stably expressed in 293 human fetal kidney cells, as was an unmodified AP protein, which served as a control. As expected, AP-PL bound to tissue sections and cells expressing the PRL receptor. Binding of AP-PL to tissues was specific and could be competed with PRL. AP-PRP-I and AP-PRP-VI did not bind to the PRL receptor. AP-PRP-I did specifically bind to the anti-mesometrial compartment of midgestation rat conceptuses. The distribution of AP-PRP-I binding in the rat conceptus suggested that AP-PRP-I was associating with the extracellular matrix (ECM). Consequently, AP-PL, AP-PRP-I, and AP-PRP-VI binding to individual components of ECMs (heparin, laminin, fibronectin, type I collagen, and type IV collagen) were evaluated. AP-PRP-I specifically bound to type IV collagen but not other ECM components. Additionally, the binding of AP-PRP-I to the rodent conceptus could be competed by type IV collagen. AP-PRP-VI exhibited week interactions with the ECM, whereas, AP-PL did not show significant binding to the ECM or ECM components. In summary, the results indicate that AP is an effective tag for monitoring the behavior of the bovine PRL family and suggest that while some PRL family members may act systemically others may be restricted to a local paracrine mode of action. (Supported by the American Heart Association, the Andrew Mellon Foundation, and the NIH, CA78312, HD37123)

KEY WORDS: bovine placental lactogen, prolactin-related protein, extracellular matrix, pregnancy