title: Alpha-lactalbumin in human milk alters the proteolytic degradation of soluble CD14 by forming a complex.
abstract: Mother's milk represents a foundational step in the proper development of newborn immunity. This is achieved, in part, through the action of numerous regulatory proteins such as soluble cluster of differentiation 14 (sCD14) found in significant quantities in human milk (~25-50 μg/mL). In adults, CD14 stimulates cytokine production in response to lipopolysaccharide (LPS), the major lipid component found in the outer membrane of Gram-negative bacteria. However, the fate and function of sCD14 in the neonatal gastrointestinal (GI) tract are unknown and may function differently from adults. Therefore, we administered human sCD14 to experimental animals and observed that it persisted in the upper GI tract after feeding. In our search for potential proteolytic protectants, immunoprecipitation of sCD14 from human milk revealed a 15-kD novel protein that copurified with sCD14. Mass spectrometry analysis of the protein identified alpha-lactalbumin. CD14 was also identified by immunoblot after immunoprecipitation of alpha-lactalbumin from milk. In vitro digestion assays revealed that purified alpha-lactalbumin decreases the proteolytic degradation of human milk derived sCD14 in vitro, suggesting a mechanism by which this key LPS receptor may remain functional in the neonate gut.
authors: Department of Biochemistry, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
authors: William J
authors: WJ
authors: Spencer
authors: Andrew
authors: A
authors: Binette
authors: Tonya L
authors: TL
authors: Ward
authors: Laura D R
authors: LD
authors: Davis
authors: David R
authors: DR
authors: Blais
authors: Joann
authors: J
authors: Harrold
authors: David R
authors: DR
authors: Mack
authors: Illimar
authors: I
authors: Altosaar
mesh_terms: D000328:Adult; D000818:Animals; D041981:Gastrointestinal Tract / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism*; D018950:Lipopolysaccharide Receptors / Q000008:administration & dosage / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D008895:Milk, Human / Q000737:chemistry*; D046912:Multiprotein Complexes / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018950:Lipopolysaccharide Receptors; D046912:Multiprotein Complexes; D007768:Lactalbumin