Lysosomal Protein Transmembrane 5 (LAPTM5)

The predicted 262-amino acid human protein is 82% identical to the mouse protein and contains 5 highly hydrophobic transmembrane domains. An antibody raised to the protein was used to show that it colocalizes with the lysosomal proteins LAMP1, LAMP2, and CD63. Western blot analysis with cell fractions from rat spleen also suggested that LAPTM5 is lysosomal. Northern blot analysis detected a 2.3-kb transcript in hematopoietic cell lines and in normal bone marrow, spleen, thymus, lymph nodes, and peripheral blood leukocytes. It was also detected in lung, where it was especially prevalent. Western blots showed an expected 29-kD protein in hematopoietic cell lines. Embryonic expression was studied using the mouse cDNA and, in contrast to adults, transcription was seen in all embryonic tissues at about equal levels.