title: Lrp5 Has a Wnt-Independent Role in Glucose Uptake and Growth for Mammary Epithelial Cells.
abstract: Lrp5 is typically described as a Wnt signaling receptor, albeit a less effective Wnt signaling receptor than the better-studied sister isoform, Lrp6. Here we show that Lrp5 is only a minor player in the response to Wnt3a-type ligands in mammary epithelial cells; instead, Lrp5 is required for glucose uptake, and glucose uptake regulates the growth rate of mammary epithelial cells in culture. Thus, a loss of Lrp5 leads to profound growth suppression, whether growth is induced by serum or by specific growth factors, and this inhibition is not due to a loss of Wnt signaling. Depletion of Lrp5 decreases glucose uptake, lactate secretion, and oxygen consumption rates; inhibition of glucose consumption phenocopies the loss of Lrp5 function. Both Lrp5 knockdown and low external glucose induce mitochondrial stress, as revealed by the accumulation of reactive oxygen species (ROS) and the activation of the ROS-sensitive checkpoint, p38α. In contrast, loss of function of Lrp6 reduces Wnt responsiveness but has little impact on growth. This highlights the distinct functions of these two Lrp receptors and an important Wnt ligand-independent role of Lrp5 in glucose uptake in mammary epithelial cells.
authors.affiliation: McArdle Laboratory for Cancer Research, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Emily N
authors.initials: EN
authors.lastname: Chin
authors.affiliation: McArdle Laboratory for Cancer Research, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Martin
authors.affiliation: McArdle Laboratory for Cancer Research, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Soyoung
authors.initials: S
authors.lastname: Kim
authors.affiliation: McArdle Laboratory for Cancer Research, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Saja A
authors.initials: SA
authors.lastname: Fakhraldeen
authors.affiliation: McArdle Laboratory for Cancer Research, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA alexander@oncology.wisc.edu.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Alexander
mesh_terms: D000818:Animals; D001692:Biological Transport; D001940:Breast / Q000166:cytology* / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D060492:Low Density Lipoprotein Receptor-Related Protein-5 / Q000378:metabolism*; D051379:Mice; D060449:Wnt Signaling Pathway
chemical_list: C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; C555483:Lrp5 protein, mouse; D005947:Glucose