Regulation and functional relevance of milk fat globules and their components in the mammary gland.
Mammary gland and epithelial cells are unique to mammals and are under the control of lactogenic hormones such as prolactin. Recent findings indicated that major components of milk fat globule membrane (MFGM) are under the control of lactogenic hormones, and that the major components butyrophilin and xanthine oxidoreductase are indispensable for milk fat secretion. Further, prolactin signaling is negatively controlled by two highly related protein tyrosine phosphatases, PTP1B and TC-PTP. Milk fat globule EGF factor 8 (MFG-E8) is one of the major components of MFGM and is upregulated during lactation. MFG-E8 is further upregulated in the involuting mammary gland. MFG-E8 on exosome-like membrane vesicles in the milk recovered from post-weaning but not lactating mammary glands exhibits higher binding activity to phosphatidylserine and apoptotic mammary epithelial cells, and serves as a link between apoptotic mammary epithelial cells and phagocytes. Recent reports using MFG-E8 deficient mice support the view that MFG-E8 is indispensable for eliminating apoptotic mammary epithelial cells during involution.
Aoki
Naohito
N
Department of Life Science, Graduate School of Bioresources, Mie University, Tsu, Japan.
D000818:Animals; D000954:Antigens, Surface / Q000502:physiology; D017209:Apoptosis / Q000502:physiology; D000071797:Butyrophilins; D005260:Female; D006017:Glycolipids / Q000378:metabolism / Q000502:physiology*; D006023:Glycoproteins / Q000378:metabolism / Q000502:physiology*; D007774:Lactation / Q000502:physiology*; D066292:Lipid Droplets; D008321:Mammary Glands, Animal / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008894:Milk Proteins / Q000378:metabolism*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases / Q000502:physiology
D000954:Antigens, Surface; D000071797:Butyrophilins; D006017:Glycolipids; D006023:Glycoproteins; D008562:Membrane Glycoproteins; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; C110367:milk fat globule; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases; C516609:Ptpn1 protein, mouse; C516653:Ptpn2 protein, mouse