The cytoplasmic tail of lysosomal acid phosphatase contains overlapping but distinct signals for basolateral sorting and rapid internalization in polarized MDCK cells.

AUTOR(ES)

Prill, V

RESUMO

Lysosomal acid phosphatase (LAP) is synthesized as a type I membrane glycoprotein and targeted to lysosomes via the plasma membrane. Its cytoplasmic tail harbours a tyrosine-containing signal for rapid internalization. Expression in Madine-Darby canine kidney cells results in direct sorting to the basolateral cell surface, rapid endocytosis and delivery to lysosomes. In contrast, a deletion mutant lacking the cytoplasmic tail is delivered to the apical plasma membrane where it accumulates before it is slowly internalized. A chimeric protein, in which the cytoplasmic tail of LAP is fused to the extracytoplasmic and transmembrane domain of the apically sorted haemagglutinin, is sorted to the basolateral plasma membrane. A series of truncation and substitution mutants in the cytoplasmic tail was constructed and comparison of their polarized sorting and internalization revealed that the determinants for basolateral sorting and rapid internalization reside in the same segment of the cytoplasmic tail. The cytoplasmic factors decoding these signals, however, tolerate distinct mutations indicating that different receptors are involved in sorting at the trans-Golgi network and at the plasma membrane.

Documentos Relacionados

• The internalization signal in the cytoplasmic tail of lysosomal acid phosphatase consists of the hexapeptide PGYRHV.
• A basolateral sorting motif in the MICA cytoplasmic tail
• Distinct pathways for basolateral targeting of membrane and secretory proteins in polarized epithelial cells.
• Replacement of the cytoplasmic domain alters sorting of a viral glycoprotein in polarized cells.
• A di-leucine motif mediates endocytosis and basolateral sorting of macrophage IgG Fc receptors in MDCK cells.