Lipocalin-interacting-membrane-receptor (LIMR) mediates cellular internalization of beta-lactoglobulin.

beta-Lactoglobulin (BLG) is a member of the lipocalin protein family and a major food-borne allergen in humans. Numerous in vitro studies have suggested a role for BLG in molecular transport processes; however, its physiological role remains enigmatic. A cellular receptor for BLG has been proposed, but has not yet been identified. Here we show that human LIMR, known to act as an endocytic receptor for lipocalin-1, also binds bovine BLG and mediates its cellular uptake. The specificity of this interaction is corroborated by a complete block of cellular uptake of BLG in the presence of LIMR antibodies or LIMR downregulation by antisense RNA. Furthermore, heterologous expression of human LIMR in insect cells mediates cellular internalization of FITC-BLG. Since LIMR is highly expressed in the human intestine, it might also function in the uptake of food-borne BLG.

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