Identification of acidic dileucine signals in LRP9 that interact with both GGAs and AP-1/AP-2.
The Golgi-localized, gamma-ear-containing, ADP ribosylation factor-binding family of monomeric clathrin adaptors (GGAs) is known to bind cargo molecules through short C-terminal peptide motifs conforming to the sequence DXXLL (X = any amino acid), while the heterotetrameric adaptors AP-1 and AP-2 utilize a similar but discrete sorting motif of the sequence [D,E]XXXL[L,I]. While it has been established that a single cargo molecule may contain either or both types of these acidic cluster-dileucine (AC-LL) sorting signals, there are no examples of cargo with overlapping GGA and AP-1/AP-2-binding motifs. In this study, we report that the cytosolic tail of low-density lipoprotein receptor-related protein (LRP)9 contains a bifunctional GGA and AP-1/AP-2-binding motif at its carboxy-terminus (EDEPLL). We further demonstrate that the internal EDEVLL sequence of LRP9 also binds to GGAs in addition to AP-2. Either AC-LL motif of LRP9 is functional in endocytosis. These findings represent the first study characterizing the trafficking of LRP9 and also have implications for the identification of additional GGA cargo molecules.
Doray
Balraj
B
Department of Internal Medicine, Washington University School of Medicine in St Louis, St Louis, MO 63110, USA.
Knisely
Jane M
JM
Wartman
Lukas
L
Bu
Guojun
G
Kornfeld
Stuart
S
D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D033961:Adaptor Protein Complex 1 / Q000378:metabolism*; D033962:Adaptor Protein Complex 2 / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D024342:Amino Acids, Acidic / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D026502:LDL-Receptor Related Proteins / Q000235:genetics / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010957:Plasmids; D011485:Protein Binding; D021382:Protein Sorting Signals; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033942:Adaptor Proteins, Vesicular Transport; D024342:Amino Acids, Acidic; C407306:GGA adaptor proteins; D026502:LDL-Receptor Related Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C102582:SORL1 protein, human; D020727:ADP-Ribosylation Factors; D007930:Leucine