LAMP1

Lysosomal-associated membrane protein 1 (LAMP-1) also known as lysosome-associated membrane glycoprotein 1 and CD107a (Cluster of Differentiation 107a), is a is_associated_with::protein that in humans is encoded by the LAMP1 is_associated_with::gene. The human LAMP1 gene is located on the long arm (q) of chromosome 13 at region 3, band 4 (13q34).

Lysosomal-associated membrane protein 1 is a glyoprotein from a family of is_associated_with::Lysosome-associated membrane glycoproteins. The LAMP-1 glycoprotein is a type I is_associated_with::transmembrane protein which is expressed at high or medium levels in at least 76 different normal tissue cell types. It resides primarily across lysosomal membranes, and functions to provide is_associated_with::selectins with is_associated_with::carbohydrate ligands. CD107a has also been shown to be a marker of is_associated_with::degranulation on is_associated_with::lymphocytes such as CD8+ and is_associated_with::NK cells. and may also play a role in is_associated_with::tumor is_associated_with::cell differentiation and is_associated_with::metastasis.

Structure
Residing primarily across lysosomal membranes, these glycoproteins consist of a large, highly glycosylated end with N-linked carbon chains on the luminal side of the membrane, and a short C-terminal tail exposed to the is_associated_with::cytoplasm. The extracytoplasmic region contains a hinge-like structure which can form is_associated_with::disulphide bridges homologous to those observed in human is_associated_with::immunoglobulin A. Other characteristics of the structure of the LAMP-1 glycoproteins include:
 * A is_associated_with::polypeptide core of ~40kDa
 * 18 {is_associated_with::N-glycosylation} sites to help with the addition of sugar chains
 * Polyactosamine attachments which protect the glyocoprotein from degradation by lysosomal is_associated_with::proteases
 * Significant quantities of polylactosaminoglycan and is_associated_with::sialic acid to traverse the trans-Golgi is_associated_with::cisternae.
 * poly-N-acetyllactosamines groups which are involved in interactions with is_associated_with::selectin and other is_associated_with::glycan-binding proteins

Function
LAMP1 and is_associated_with::LAMP2 glycoproteins comprise 50% of all lysosomal membrane proteins, and are thought to be responsible in part for maintaining lysosomal integreity, pH and is_associated_with::catabolism. The expression of LAMP1 and LAMP2 glycoproteins are linked, as deficiencies in LAMP1 gene will lead to increased expression of LAMP2 glycoproteins. The two are therefore thought to share similar functions in vivo. However, this makes the determining the precise function of LAMP1 difficult, because while the LAMP1 deficient is_associated_with::phenotype is little different than the wild type due to LAMP2 up regulation, the LAMP1/LAMP2 double deficient phenotype leads to is_associated_with::embryonic lethality.

Although the LAMP1 glycoproteins primarily reside across lysosomal membranes, in certain cases they can be expressed across the plasma membrane of the cell. Expression of LAMP1 at the cell surface can occur due to lysosomal fusion with the cell membrane. Cell surface expression of LAMP1 can serve as a ligand for is_associated_with::selectins and help mediate cell-is_associated_with::cell adhesion. Accordingly, cell surface expression of LAMP1 is seen in cells with migratory or invasive functions, such as is_associated_with::cytotoxic T cells, is_associated_with::platelets and is_associated_with::macrophages. Cell surface expression of LAMP1 and LAMP2 is also often seen in is_associated_with::cancer cells, particularly cancers with high metastatic potential, such as colon carcinoma and melanoma, and has been shown to correlate with their metastatic potential.

Role in cancer
LAMP1 expression on the surface of tumor cells has been observed for a number of different cancer types, particularly in highly metastatic cancers such as is_associated_with::pancreatic cancer, is_associated_with::colon cancer  and is_associated_with::melanoma. The structure of LAMP1 correlates with differentiation and metastatic potential of tumor cells as it is thought to help mediate cell-cell adhesion and migration. Indeed, the adhesion of some cancer cells to the is_associated_with::extracellular matrix is mediated by interactions between LAMP1 and LAMP2 and is_associated_with::E-selectin and is_associated_with::galectins, with the LAMPs serving as ligands for the cell-adhesion molecules.

Cell membrane expression of LAMP-1 observed in the following cancer types:
 * Human is_associated_with::fibrosarcoma,
 * Colon adenocarcinoma,
 * is_associated_with::Melanoma,
 * Pancreatic adenocarcinoma, and
 * is_associated_with::Astrocytoma.