Biology:LAMP2

Short description: Protein-coding gene in the species Homo sapiens

Generic protein structure example

Lysosome-associated membrane protein 2 (LAMP2), also known as CD107b (Cluster of Differentiation 107b) and Mac-3, is a human gene. Its protein, LAMP2, is one of the lysosome-associated membrane glycoproteins.

The protein encoded by this gene is a member of a family of membrane glycoproteins. This glycoprotein provides selectins with carbohydrate ligands. It may play a role in tumor cell metastasis. It may also function in the protection, maintenance, and adhesion of the lysosome. Alternative splicing of the gene produces three variants - LAMP-2A, LAMP-2B and LAMP-2C. LAMP-2A is the receptor for chaperone-mediated autophagy. Recently it has been determined that antibodies against LAMP-2 account for a fraction of patients who get a serious kidney disease termed focal necrotizing glomerulonephritis.

LAMP-2B is associated with Danon disease.

Structure and tissue distribution

The gene for LAMP2 has 9 coding exons and 2 alternate last exons, 9a and 9b. When the last exon is spliced with the alternative exon, it is a variant called LAMP2b, which varies in the last 11 amino acids of its C-terminal sequence: in the luminal domain, the transmembrane domain, and the cytoplasmic tail. The original (LAMP2a) is highly expressed in the placenta, lung, and liver, while LAMP2b is highly expressed in skeletal muscle.

Function

Lysosomes are cell organelles found in most animal cells. Their main functions center around breaking down materials and debris in the cell. Some of this is done via acid hydrolases that degrade foreign materials and have specialized autolytic functions. These hydrolyses are stored in the lysosomal membrane, which also house lysosomal membrane glycoproteins.

LAMP1 and LAMP2 make up about 50% of lysosomal membrane glycoproteins. (See LAMP1 for more information on both LAMP1 and LAMP2.) Both of these consist of polypeptides of about 40 kD, with the core polypeptide surrounded by 16 to 20 attached N-linked saccharides. The biological functions of these glycoproteins are disputed. They are believed to be significantly involved in operations of the lysosomes, including maintaining integrity, pH and catabolism. Further, some of the functions of LAMP2 are believed to be protecting the lysosomal membrane from proteolytic enzymes that are within the lysosome itself (as in autodigestion), acting as a receptor into the lysosome for proteins, adhesion (when expressed on the outside surface of the plasma membrane) and signal transduction, both inter- and intra-. It also provides protection for the cell from methylating mutagens.

Role in cancer

LAMP2 has been specifically implicated in tumor cell metastasis. Both LAMP1 and LAMP2 have been found expressed on the surface of cancerous tumors, specifically in cells of highly metastatic cancer such as colon cancer and melanoma. They are rarely found on the plasma membranes of normal cells, and are found more on highly metastatic tumors than on poorly metastatic ones. LAMP2, along with LAMP1, interact with E-selectin and galectins to mediate the adhesion of some cancer cells to the ECM. The two LAMP molecules act as ligands for the cell-adhesion molecules.

It has also been shown that the down-regulation of LAMP2 could both reduce the resistance of breast cancer cells to the paclitaxel and could inhibit cell proliferation in multiple myeloma cells.

Along with other genes such as LC3B, p62 and CTSB, a strong up regulation of LAMP2 was detected in perinecrotic areas of glioblastomas. This suggests autophagy induction in gliomas could be caused by micro-environmental changes.

In a study of glial tumors, the cell membranes of glial and endothelial cells were found to contain LAMP1 and LAMP2, while YKL-40 (a different glycoprotein) was found in the cytoplasm. This suggests that the three glycoproteins are involved in tumor development, specifically in the processes of angiogenesis and tissue remodeling.

Inducers

• CA77.1
• QX39

See also

• Cluster of differentiation

Further reading

• "CD107a (LAMP-1) and CD107b (LAMP-2)". Journal of Biological Regulators and Homeostatic Agents 16 (2): 147–51. 2003. PMID 12144129. 
• "Confirmation of the chromosomal localization of human lamp genes and their exclusion as candidate genes for Salla disease". Human Genetics 88 (1): 95–7. November 1991. doi:10.1007/BF00204936. PMID 1959930. 
• "The nucleotide sequence of a CpG island demonstrates the presence of the first exon of the gene encoding the human lysosomal membrane protein lamp2 and assigns the gene to Xq24". Genomics 9 (3): 551–4. March 1991. doi:10.1016/0888-7543(91)90424-D. PMID 2032724. 
• "The polylactosaminoglycans of human lysosomal membrane glycoproteins lamp-1 and lamp-2. Localization on the peptide backbones". The Journal of Biological Chemistry 265 (33): 20488–95. November 1990. doi:10.1016/S0021-9258(17)30530-6. PMID 2243102. 
• "Two human lysosomal membrane glycoproteins, h-lamp-1 and h-lamp-2, are encoded by genes localized to chromosome 13q34 and chromosome Xq24-25, respectively". The Journal of Biological Chemistry 265 (13): 7548–51. May 1990. doi:10.1016/S0021-9258(19)39148-3. PMID 2332441. 
• "Purification and characterization of human lysosomal membrane glycoproteins". Archives of Biochemistry and Biophysics 268 (1): 360–78. January 1989. doi:10.1016/0003-9861(89)90597-3. PMID 2912382. 
• "Cloning of cDNAs encoding human lysosomal membrane glycoproteins, h-lamp-1 and h-lamp-2. Comparison of their deduced amino acid sequences". The Journal of Biological Chemistry 263 (35): 18920–8. December 1988. doi:10.1016/S0021-9258(18)37370-8. PMID 3198605. 
• "The lysosomal membrane glycoproteins Lamp-1 and Lamp-2 are present in mobilizable organelles, but are absent from the azurophil granules of human neutrophils". The Biochemical Journal 311 (2): 667–74. October 1995. doi:10.1042/bj3110667. PMID 7487911. 
• "An alternatively spliced form of the human lysosome-associated membrane protein-2 gene is expressed in a tissue-specific manner". Biochemical and Biophysical Research Communications 215 (2): 757–67. October 1995. doi:10.1006/bbrc.1995.2528. PMID 7488019. 
• "Complete cDNA sequence of human lysosome-associated membrane protein-2". Biochemical and Biophysical Research Communications 205 (1): 1–5. November 1994. doi:10.1006/bbrc.1994.2620. PMID 7999007. 
• "Assignment of O-glycan attachment sites to the hinge-like regions of human lysosomal membrane glycoproteins lamp-1 and lamp-2". Archives of Biochemistry and Biophysics 304 (1): 65–73. July 1993. doi:10.1006/abbi.1993.1322. PMID 8323299. 
• "The genes of major lysosomal membrane glycoproteins, lamp-1 and lamp-2. 5'-flanking sequence of lamp-2 gene and comparison of exon organization in two genes". The Journal of Biological Chemistry 268 (12): 9014–22. April 1993. doi:10.1016/S0021-9258(18)52972-0. PMID 8517882. 
• "Lysosome-associated membrane proteins h-LAMP1 (CD107a) and h-LAMP2 (CD107b) are activation-dependent cell surface glycoproteins in human peripheral blood mononuclear cells which mediate cell adhesion to vascular endothelium". Cellular Immunology 171 (1): 10–9. July 1996. doi:10.1006/cimm.1996.0167. PMID 8660832. 
• "The lysosomal granule membrane protein, LAMP-2, is also present in platelet dense granule membranes". Thrombosis and Haemostasis 75 (4): 623–9. April 1996. doi:10.1055/s-0038-1650333. PMID 8743190. 
• "Distribution and subcellular localization of a lysosome-associated protein in human genital organs". Cell and Tissue Research 287 (2): 335–42. February 1997. doi:10.1007/s004410050758. PMID 8995204. 
• "Biosynthetic transport of a major lysosome-associated membrane glycoprotein 2, lamp-2: a significant fraction of newly synthesized lamp-2 is delivered to lysosomes by way of early endosomes". Journal of Biochemistry 120 (6): 1088–94. December 1996. doi:10.1093/oxfordjournals.jbchem.a021526. PMID 9010755. 
• "Sorting of lysosomal membrane glycoproteins lamp-1 and lamp-2 into vesicles distinct from mannose 6-phosphate receptor/gamma-adaptin vesicles at the trans-Golgi network". The Journal of Biological Chemistry 273 (30): 18966–73. July 1998. doi:10.1074/jbc.273.30.18966. PMID 9668075. 
• "Infection of epithelial cells by pathogenic neisseriae reduces the levels of multiple lysosomal constituents". Infection and Immunity 66 (10): 5001–7. October 1998. doi:10.1128/IAI.66.10.5001-5007.1998. PMID 9746610. 
• "Differential expression of the lysosome-associated membrane proteins in normal human tissues". Archives of Biochemistry and Biophysics 365 (1): 75–82. May 1999. doi:10.1006/abbi.1999.1147. PMID 10222041. 
• "Primary LAMP-2 deficiency causes X-linked vacuolar cardiomyopathy and myopathy (Danon disease)". Nature 406 (6798): 906–10. August 2000. doi:10.1038/35022604. PMID 10972294. Bibcode: 2000Natur.406..906N. 

External links

• LAMP2+protein,+human at the US National Library of Medicine Medical Subject Headings (MeSH)
• PDBe-KB provides an overview of all the structure information available in the PDB for Human Lysosome-associated membrane glycoprotein 2

This article incorporates text from the United States National Library of Medicine, which is in the public domain.