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Molecular Determinants of Milk Lipid Secretion

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Abstract

Mammary epithelial cells secrete lipids by an envelopment process that produces lipid droplets coated by membranes derived from the plasma membrane and possibly secretory vesicles. This secretion process, which resembles viral budding, is hypothesized to be mediated by specific interactions between molecules on the surface of intracellular lipids and membrane elements of the cell. Multiple lines of evidence indicate that milk lipid secretion occurs through a tripartite complex between the integral transmembrane protein, butyrophilin (BTN); the soluble metabolic enzyme, xanthine oxidoreductase (XOR); and the lipid droplet surface protein, adipophilin (ADPH). However, topological evidence from freeze-fracture replica immunolabelling (FRIL) challenge this model and suggests that milk lipid secretion is mediated by butyrophilin alone. Advances in our understanding of the molecular, structural, and functional properties of these proteins now make it possible to understand the physiological functions of each of these molecules in detail and to identify the specific molecular determinants that mediate milk lipid secretion.

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Acknowledgments

JLM was supported by NIH grants P01 HD038129 and R01 HD045965. TDR was supported by a UNCF-Merck Graduate Science Initiative fellowship.

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Authors and Affiliations

  1. Department of Obstetrics and Gynecology, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    James L. McManaman & Tanya D. Russell

  2. Department of Physiology and Biophysics, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    James L. McManaman

  3. Department of Microbiology, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    Jerome Schaack

  4. Department of Pathology, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    David J. Orlicky

  5. Graduate Program in Molecular Biology, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    James L. McManaman, Tanya D. Russell & Jerome Schaack

  6. Graduate Program in Reproductive Sciences, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    James L. McManaman

  7. Graduate Program in Cell Biology, Stem Cells and Development, University of Colorado Denver and Health Sciences Center, Aurora, CO, USA

    James L. McManaman

  8. Leibniz Institute for Arteriosclerosis Research, University of Munster, Munster, Germany

    Horst Robenek

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  1. James L. McManaman
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Correspondence to James L. McManaman.

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McManaman, J.L., Russell, T.D., Schaack, J. et al. Molecular Determinants of Milk Lipid Secretion. J Mammary Gland Biol Neoplasia 12, 259–268 (2007). https://doi.org/10.1007/s10911-007-9053-5

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  • DOI: https://doi.org/10.1007/s10911-007-9053-5

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