Presenilin/γ-Secretase-mediated Cleavage Regulates Association of Leukocyte-Common Antigen-related (LAR) Receptor Tyrosine Phosphatase with β-Catenin

Annakaisa Haapasalo, Doo Yeon Kim, Bryce W. Carey, Mari K. Turunen, Warren H. Pettingell, Dora M. Kovacs
2007 Journal of Biological Chemistry  
Leukocyte-common antigen-related (LAR) receptor tyrosine phosphatase regulates cell adhesion and formation of functional synapses and neuronal networks. Here we report that LAR is sequentially cleaved by ␣and presenilin (PS)/␥-secretases, which also affect signaling and/or degradation of type-I membrane proteins including the Alzheimer disease-related ␤-amyloid precursor protein. Similar to the previously characterized PS/␥-secretase substrates, inhibition of ␥-secretase activity resulted in
more » ... vity resulted in elevated LAR C-terminal fragment (LAR-CTF) levels in stably LAR-overexpressing Chinese hamster ovary (CHO) cells, human neuroglioma cells, and mouse cortical neurons endogenously expressing LAR. Furthermore, LAR-CTF levels increased in cells lacking functional PS, indicating that ␥-secretase-mediated cleavage of LAR was PS-dependent. Inhibition of ␣-secretase activity by TAPI-1 treatment blocked LAR-CTF accumulation, demonstrating that prior ectodomain shedding was prerequisite for PS/␥-secretase-mediated cleavage of LAR. Moreover, we identified the product of PS/␥-secretase cleavage, LAR intracellular domain (LICD), both in vitro and in cells overexpressing full-length (FL) LAR or LAR-CTFs. LAR localizes to cadherin-␤-catenin-based cellular junctions. Assembly and disassembly of these junctions are regulated by tyrosine phosphorylation. We found that endogenous tyrosine-phosphorylated ␤-catenin coimmunoprecipitated with LAR in CHO cells. However, when PS/␥-secretase activity was inhibited, the association between LAR and ␤-catenin significantly diminished. In addition to cell adhesion, ␤-catenin is involved in transcriptional regulation. We observed that LICD significantly decreased transcription of cyclin D1, one of the ␤-catenin target genes. Thus, our results show that PS/␥-secretase-mediated cleavage of LAR controls LAR-␤-catenin interaction, suggesting an essential role for PS/␥-secretase in the regulation of LAR signaling. Presenilin (PS) 2 /␥-secretase is a high molecular weight enzymatic complex composed of PS1 or PS2, nicastrin, Aph-1, and Pen-2 (1-5). PS/␥-secretase plays a key role in the pathogenesis of Alzheimer disease (AD) by cleaving ␤-amyloid precursor protein (APP) by regulated intramembraneous processing (RIP) at two adjacent sites (6 -8). Following ectodomain shedding of APP, the ␥-cleavage generates the A␤-peptide, the major constituent of amyloid plaques in AD brain, and a small p3 fragment. The product of the ⑀-cleavage is the APP intracellular domain (AICD) (9 -11). APP ectodomain shedding is mediated by either ␣-secretases of the ADAM family metalloproteases (12, 13) or BACE (␤-site APP cleaving enzyme) (14 -17), producing membrane-bound APP C-terminal fragments (CTFs). In addition to APP, other type-I membrane proteins are known to undergo PS/␥-secretase-mediated RIP (18). Among these are Notch (8), cadherins (19), nectin-1␣ (20), and voltagegated sodium channel ␤2-subunit (21, 22). Similar to APP, these proteins undergo ectodomain shedding prior to ␥-secretase-mediated cleavage and release intracellular domains (ICDs) as C-terminal products. Typically, loss of PS function or lack of PS/␥-secretase activity results in increased levels of membrane-associated CTFs (23-25). LAR (leukocyte-common antigen-related) phosphatase (26, 27) is a type-I transmembrane protein and a member of the receptor protein tyrosine phosphatase (RPTP) family. The RPTP family phosphatases play pleiotropic roles in both developing and adult nervous system, including regulation of cell adhesion, formation and maintenance of synaptic connections, and learning and memory (28). The adhesion molecule-like LAR ectodomain contains immunoglobulin (IgG)-like and fibronectin type-III domains. The transmembrane domain is followed by two cytosolic phosphatase domains (D1 and D2), of . 2 The abbreviations used are: PS, presenilin; Aph-1, anterior pharynx defective 1 homologue; Pen-2, presenilin enhancer 2 homologue; LAR, leukocytecommon antigen-related phosphatase; CTF, C-terminal fragment; CHO, Chinese hamster ovary; LICD, LAR intracellular domain; AD, Alzheimer disease; APP, ␤-amyloid precursor protein; ADAM, a disintegrin and metalloproteinase domain; RPTP, receptor protein tyrosine phosphatase; FL, full-
doi:10.1074/jbc.m611324200 pmid:17259169 fatcat:w2mneubp6rhqvmnf5lqgbdutdy