James L. McManaman, Ph.D.

James L. McManaman

Assistant Professor

Joint Appointments: Physiology and Biophysics, University of Colorado Cancer Center 

Ph.D. 1978 Chemistry and Biochemistry, University of Colorado, Boulder

Telephone:            303-315-7093

Email:             jim.mcmanaman@uchsc.edu

The research in my laboratory focuses on two general areas; the regulation of cytoplasmic lipid droplet formation and secretion by mammary epithelial cells and the role of oxygen radical generating enzymes in breast cancer.  These two interests are linked by the enzyme xanthine oxidoreductase (XOR).   This enzyme is an obligate oxygen radical generator, capable of acting on wide variety of organic compounds, including potentially carcinogenic as well as chemotherapeutic agents.  One of the substrates that XOR is able to oxidize is acetaldehyde, the end product of alcohol metabolism.  This is of particular interest in breast cancer, since XOR activity has been linked to the generation of genotoxic radicals as a consequence of alcohol metabolism, and there is a positive correlation with alcohol consumption and the incidence of oxygen radical damaged DNA in breast tissue.  The oxygen radical generating capacity of XOR is regulated by the redox properties of its sulfhydryls and linked to conformational changes in its structure.  Disulfide oxidized XOR is the primary oxygen radical generating form and mammary tissue possesses an enzyme capable of converting XOR to this radical generating form.  Structural analysis has shown that this conversion leads to exposure of a hydrophobic domain on XOR that may allow the enzyme to interact with cellular membranes, providing a potential localized source of cytotoxic oxygen radicals. 

Cytoplasmic lipid droplets are the immediate precursors of milk lipids - a primary nutritional source for many mammalian neonates, including humans.  Lipid droplet secretion occurs by a novel mechanism of membrane envelopment and budding of these structures.  XOR may play an important role in this process by forming a tripartite complex with the lipid storage droplet coat protein – adipophilin (ADPH) and the mammary specific transmembrane protein - butyrophilin (Btn) at the plasma membrane.  The membrane association of XOR is dynamically linked to the secretory activity of the mammary gland and a secreted complex of XOR, ADPH and Btn is found on membranes surrounding secreted lipid droplets.  Our current efforts are aimed at understanding how this complex is formed and how it functions in lipid secretion. 

Cytoplasmic lipid droplet formation is also one of the earliest phenotypes of differentiating mammary epithelial cells.  The formation of similar droplets is thought to be regulated by ADPH in many cell types.  During mammary gland differentiation these droplets selectively accumulate in mammary epithelial cells and this accumulation is linked to increased ADPH expression.  Molecular studies in cultured cells indicate that specific structural regions of ADPH are responsible for regulating accumulation of these structures and studies are underway to establish the physiological functions of ADPH in both the formation and secretion of lipid storage droplets and to delineate the underlying structural basis for these functions.  

Selected Publications:

            McManaman, J.L., Neville, M.C. and Wright R.M. Mouse mammary gland xanthine oxidoreductase: Purification, characterization and regulation.   Arch. Biochem. Biophys. 371: 308-316, 1999 

            Wu, C.C., Howell, K.E., Neville, M.C., Yates, J.R., and McManaman, J.L. Proteomics reveal contribution of endoplasmic reticulum membranes to the lipid secretion process in mammary epithelial cells.  Electrophoresis 21: 3470-3482, 2000

            McManaman, J.L. and Bain, D.L., Structural and conformational analysis of the oxidase to dehydrogenase conversion of xanthine oxidoreductase. J. Biol. Chem. 277, 21261-21268, 2002

McManaman, J.L., Palmer, C.A., Wright, R.M. and Neville, M.C., Functional regulation of xanthine oxidoreductase expression and localization in mammary epithelial cells: Evidence of a role in lipid secretion.  J. Physiol., 545: 567-579, 2002

            Palmer, C.A., Lubon, H. and McManaman, J.L.  Transgenic mice expressing recombinant human protein C exhibit defects in lactation and impaired mammary gland development. Transgenic Res. (In Press) 2003

 McManaman, J.L. and Neville, M.C.  Mammary physiology and milk secretion. Advances in Drug Deliver Research (In press) 2003

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