The epidermal growth factor receptor juxtamembrane domain has multiple basolateral plasma membrane localization determinants, including a dominant signal with a polyproline core.
The epidermal growth factor (EGF) receptor is located predominantly in the basolateral membrane of polarized epithelia, where it plays a pivotal role during organogenesis and tissue homeostasis. We have shown previously that a 22-amino acid sequence in the EGF receptor juxtamembrane domain contains autonomous sorting information necessary for basolateral localization using the Madin-Darby canine kidney epithelial cell model. The goal of this study was to determine the molecular basis of EGF receptor basolateral membrane expression using site-directed mutagenesis to modify specific residues in this region. We now show that this sequence has two different, functionally redundant basolateral sorting signals with distinct amino acid requirements: one dependent on residues (658)LL(659) conforming to well-characterized leucine-based sorting signals, and a second containing a polyproline core comprising residues Pro(667) and Pro(670) ((667)PXXP(670)). Our data also suggest that Arg(662) contributes to the function of the proline-based signal. (667)PXXP(670) was the dominant signal when both motifs were present and was more effective than (658)LL(659) at overriding strong apical sorting signals located in the same molecule. Site-directed mutations at Arg(662), Pro(667), and Pro(670) were also associated with increased apical expression of full-length EGF receptors, demonstrating for the first time that the juxtamembrane region is necessary for accurate polarized expression of the native molecule.
He
Cheng
C
Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Hobert
Michael
M
Friend
Leslie
L
Carlin
Cathleen
C
D000595:Amino Acid Sequence; D001345:Autoradiography; D002460:Cell Line; D016764:Cell Polarity; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011392:Proline / Q000378:metabolism*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary
D021382:Protein Sorting Signals; D011392:Proline; D066246:ErbB Receptors