Intracellular sorting and targeting of melanosomal membrane proteins: Identification of signals for sorting of the human brown locus protein, GP75 Journal Article
| Authors: | Vijayasaradhi, S.; Xu, Y.; Bouchard, B.; Houghton, A. N. |
| Article Title: | Intracellular sorting and targeting of melanosomal membrane proteins: Identification of signals for sorting of the human brown locus protein, GP75 |
| Abstract: | The structural and functional integrity of cytoplasmic organelles is maintained by intracellular mechanisms that sort and target newly synthesized proteins to their appropriate cellular locations. In melanocytic cells, melanin pigment is synthesized in specialized organelles, melanosomes. A family of melanocyte-specific proteins, known as tyrosinase-related proteins that regulate melanin pigment synthesis, is localized to the melanosomal membrane. The human brown locus protein, tyrosinase-related protein-1 or gp75, is the most abundant glycoprotein in melanocytic cells, and is a prototype for melanosomal membrane proteins. To investigate the signals that allow intracellular retention and sorting of glycoprotein (gp)75, we constructed protein chimeras containing the amino-terminal extracellular domain of the T lymphocyte surface protein CDS, and transmembrane and cytoplasmic domains of gp75. In fibroblast transfectants, chimeric CD8 molecules containing the 36-amino acid cytoplasmic domain of gp75 were retained in cytoplasmic organelles. Signals in the gp75 cytoplasmic tail alone, were sufficient for intracellular retention and targeting of the chimeric proteins to the endosomal/lysosomal compartment. Analysis of subcellular localization of carboxyl-terminal deletion mutants of gp75 and the CD8/gp75 chimeras showed that deletion of up to 20 amino acids from the gp75 carboxyl terminus did not affect intracellular retention and sorting, whereas both gp75 and CD8/gp75 mutants lacking the carboxyl-terminal 27 amino acids were transported to the cell surface. This region contains the amino acid sequence, asn-gln-pro-leu-leu-thr, and this hexapeptide is conserved among other melanosomal proteins. Further evidence showed that this hexapeptide sequence is necessary for intracellular sorting of gp75 in melanocytic cells, and suggested that a signal for sorting melanosomal proteins along the endosomal/lysosomal pathway lies within this sequence. These data provide evidence for common signals for intracellular sorting of melanosomal and lysosomal proteins, and support the notion that lysosomes and melanosomes share a common endosomal pathway of biogenesis. |
| Keywords: | signal transduction; unclassified drug; human cell; sequence deletion; protein domain; cd8 antigen; t lymphocyte; animal; mice; melanoma; melanocytes; carboxy terminal sequence; protein targeting; tumor cells, cultured; transfection; structure-activity relationship; fluorescent antibody technique; amino acid sequence; conserved sequence; molecular sequence data; sequence homology, amino acid; species specificity; amino terminal sequence; membrane glycoproteins; membrane protein; melanoma cell; fibroblasts; cytoplasm; base sequence; microscopy, fluorescence; dna mutational analysis; glycoprotein; biological transport; deletion mutant; lysosome; antigens, cd8; chimeric protein; endosome; melanosome; microscopy, immunoelectron; human; priority journal; article; cell compartmentation; support, u.s. gov't, p.h.s.; glycoprotein gp 75; chimeric proteins |
| Journal Title: | Journal of Cell Biology |
| Volume: | 130 |
| Issue: | 4 |
| ISSN: | 0021-9525 |
| Publisher: | Rockefeller University Press |
| Date Published: | 1995-08-15 |
| Start Page: | 807 |
| End Page: | 820 |
| Language: | English |
| DOI: | 10.1083/jcb.130.4.807 |
| PUBMED: | 7642699 |
| PROVIDER: | scopus |
| PMCID: | PMC2199968 |
| DOI/URL: | |
| Notes: | Article -- Export Date: 28 August 2018 -- Source: Scopus |
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