Exp Mol Med.  2014 Apr;46(4):e89. 10.1038/emm.2013.161.

Tetraspanin CD9 modulates ADAM17-mediated shedding of LR11 in leukocytes

• Tsukamoto
• Takeuchi M
• Kawaguchi
• Togasaki E
• Yamazaki A
• Sugita Y
• Muto T
• Sakai S
• Takeda Y
• Ohwada C
• Sakaida E
• Shimizu N
• Nishii K
• Jiang M
• Yokote K
• Bujo H
• Nakaseko C

• KMID: 2155354
• DOI: http://doi.org/10.1038/emm.2013.161

Abstract

LR11, also known as SorLA or SORL1, is a type-I membrane protein from which a large extracellular part, soluble LR11 (sLR11), is released by proteolytic shedding on cleavage with a disintegrin and metalloproteinase 17 (ADAM17). A shedding mechanism is presumed to have a key role in the functions of LR11, but the evidence for this has not yet been demonstrated. Tetraspanin CD9 has been recently shown to regulate the ADAM17-mediated shedding of tumor necrosis factor-alpha and intercellular adhesion molecule-1 on the cell surface. Here, we investigated the role of CD9 on the shedding of LR11 in leukocytes. LR11 was not expressed in THP-1 monocytes, but it was expressed and released in phorbol 12-myristate 13-acetate (PMA)-induced THP-1 macrophages (PMA/THP-1). Confocal microscopy showed colocalization of LR11 and CD9 proteins on the cell surface of PMA/THP-1. Ectopic neo-expression of CD9 in CCRF-SB cells, which are LR11-positive and CD9-negative, reduced the amount of sLR11 released from the cells. In contrast, incubation of LR11-transfected THP-1 cells with neutralizing anti-CD9 monoclonal antibodies increased the amount of sLR11 released from the cells. Likewise, the PMA-stimulated release of sLR11 increased in THP-1 cells transfected with CD9-targeted shRNAs, which was negated by treatment with the metalloproteinase inhibitor GM6001. These results suggest that the tetraspanin CD9 modulates the ADAM17-mediated shedding of LR11 in various leukemia cell lines and that the association between LR11 and CD9 on the cell surface has an important role in the ADAM17-mediated shedding mechanism.

Keyword

ADAM17; CD9; LR11; TNF-alpha converting enzyme; Tetraspanin

MeSH Terms

ADAM Proteins/*metabolism
Antigens, CD9/genetics/*metabolism
Cell Line, Tumor
Humans
LDL-Receptor Related Proteins/genetics/*metabolism
Leukocytes/*metabolism
Macrophages/metabolism
Membrane Transport Proteins/genetics/*metabolism
Proteolysis
ADAM Proteins
Antigens, CD9
LDL-Receptor Related Proteins
Membrane Transport Proteins