Monotreme lactation protein is highly expressed in monotreme milk and provides antimicrobial protection.

Autor:	Enjapoori AK; School of Medicine, Deakin University, Geelong, Victoria, Australia aenjapoo@deakin.edu.au., Grant TR; School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia., Nicol SC; School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia., Lefèvre CM; School of Medicine, Deakin University, Geelong, Victoria, Australia., Nicholas KR; School of Medicine, Deakin University, Geelong, Victoria, Australia Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia., Sharp JA; School of Medicine, Deakin University, Geelong, Victoria, Australia Institute for Frontier Materials, Deakin University, Geelong, Victoria, Australia.
Jazyk:	angličtina
Zdroj:	Genome biology and evolution [Genome Biol Evol] 2014 Sep 22; Vol. 6 (10), pp. 2754-73. Date of Electronic Publication: 2014 Sep 22.
DOI:	10.1093/gbe/evu209
Abstrakt:	Monotremes (platypus and echidna) are the descendants of the oldest ancestor of all extant mammals distinguished from other mammals by mode of reproduction. Monotremes lay eggs following a short gestation period and after an even briefer incubation period, altricial hatchlings are nourished over a long lactation period with milk secreted by nipple-less mammary patches located on the female's abdomen. Milk is the sole source of nutrition and immune protection for the developing young until weaning. Using transcriptome and mass spectrometry analysis of milk cells and milk proteins, respectively, a novel Monotreme Lactation Protein (MLP) was identified as a major secreted protein in milk. We show that platypus and short-beaked echidna MLP genes show significant homology and are unique to monotremes. The MLP transcript was shown to be expressed in a variety of tissues; however, highest expression was observed in milk cells and was expressed constitutively from early to late lactation. Analysis of recombinant MLP showed that it is an N-linked glycosylated protein and biophysical studies predicted that MLP is an amphipathic, α-helical protein, a typical feature of antimicrobial proteins. Functional analysis revealed MLP antibacterial activity against both opportunistic pathogenic Staphylococcus aureus and commensal Enterococcus faecalis bacteria but showed no effect on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Salmonella enterica. Our data suggest that MLP is an evolutionarily ancient component of milk-mediated innate immunity absent in other mammals. We propose that MLP evolved specifically in the monotreme lineage supporting the evolution of lactation in these species to provide bacterial protection, at a time when mammals lacked nipples. (© The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.)
Databáze:	MEDLINE
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