Activation and functional characterization of the mosaic receptor SorLA/LR11.
We previously isolated and sequenced the approximately 250-kDa type 1 receptor sorLA/LR11, a mosaic protein with elements characterizing the Vps10p domain receptor family as well as the low density lipoprotein receptor family. The N terminus of the Vps10p domain comprises a consensus sequence for cleavage by furin ((50)RRKR(53)) that precedes a truncation found in sorLA isolated from human brain. Here we show that sorLA, like sortilin-1/neurotensin receptor-3, whose lumenal domain consists of a Vps10p domain only, is synthesized as a proreceptor that is cleaved by furin in late Golgi compartments. We show that the truncation conditions the Vps10p domain for propeptide inhibitable binding of neuropeptides and the receptor-associated protein. We further demonstrate that avid binding of the receptor-associated protein, apolipoprotein E, and lipoprotein lipase not inhibited by propeptide occurs to sites located in other lumenal domains. In transfected cells, about 10% of full-length sorLA were expressed on the cell surface capable of mediating endocytosis. However, the major pool of receptors was found in late Golgi compartments, suggesting possible interaction with newly synthesized ligands. The results show that sorLA, following activation by truncation, binds multiple ligands and may mediate both endocytosis and sorting.
Jacobsen
L
L
Department of Medical Biochemistry, University of Aarhus, DK-8000, Aarhus C, Denmark.
Madsen
P
P
Jacobsen
C
C
Nielsen
M S
MS
Gliemann
J
J
Petersen
C M
CM
D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D017931:DNA Primers; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D045683:Furin; D006056:Golgi Apparatus / Q000378:metabolism; D006868:Hydrolysis; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013381:Subtilisins / Q000378:metabolism; D033921:Vesicular Transport Proteins; D000099183:Sortilin
D033942:Adaptor Proteins, Vesicular Transport; D017931:DNA Primers; D005656:Fungal Proteins; D045683:Furin; D008024:Ligands; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D029701:Saccharomyces cerevisiae Proteins; D013381:Subtilisins; D033921:Vesicular Transport Proteins; D000099183:Sortilin; C087335:PEP1 protein, S cerevisiae