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Apolipoprotein D Internalization Is a Basigin-dependent Mechanism
#MMPMID25918162
Najyb O
; Brissette L
; Rassart E
J Biol Chem
2015[Jun]; 290
(26
): 16077-87
PMID25918162
show ga
Apolipoprotein D (apoD), a member of the lipocalin family, is a 29-kDa secreted
glycoprotein that binds and transports small lipophilic molecules. Expressed in
several tissues, apoD is up-regulated under different stress stimuli and in a
variety of pathologies. Numerous studies have revealed that overexpression of
apoD led to neuroprotection in various mouse models of acute stress and
neurodegeneration. This multifunctional protein is internalized in several cells
types, but the specific internalization mechanism remains unknown. In this study,
we demonstrate that the internalization of apoD involves a specific cell surface
receptor in 293T cells, identified as the transmembrane glycoprotein basigin
(BSG, CD147); more particularly, its low glycosylated form. Our results show that
internalized apoD colocalizes with BSG into vesicular compartments.
Down-regulation of BSG disrupted the internalization of apoD in cells. In
contrast, overexpression of basigin in SH-5YSY cells, which poorly express BSG,
restored the uptake of apoD. Cyclophilin A, a known ligand of BSG, competitively
reduced apoD internalization, confirming that BSG is a key player in the apoD
internalization process. In summary, our results demonstrate that basigin is very
likely the apoD receptor and provide additional clues on the mechanisms involved
in apoD-mediated functions, including neuroprotection.
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