Insulin-like Growth Factor-1 (IGF-1)-induced Processing of Amyloid-β Precursor Protein (APP) and APP-like Protein 2 Is Mediated by Different Metalloproteinases

Abstract

␣-Secretase cleavage of the amyloid precursor protein (APP) is of great interest because it prevents the formation of the Alzheimer-linked amyloid-␤ peptide. APP belongs to a conserved gene family including the two paralogues APP-like protein (APLP) 1 and 2. Insulin-like growth factor-1 (IGF-1) stimulates the shedding of all three proteins. IGF-1-induced shedding of both APP and APLP1 is dependent on phosphatidylinositol 3-kinase (PI3-K), whereas APLP2 shedding is independent of this signaling pathway. Here, we used human neuroblastoma SH-SY5Y cells to investigate the involvement of protein kinase C (PKC) in the proteolytic processing of endogenously expressed members of the APP family. Processing was induced by IGF-1 or retinoic acid, another known stimulator of APP ␣-secretase shedding. Our results show that stimulation of APP and APLP1 processing involves multiple signaling pathways, whereas APLP2 processing is mainly dependent on PKC. Next, we wanted to investigate whether the difference in the regulation of APLP2 shedding compared with APP shedding could be due to involvement of different processing enzymes. We focused on the two major ␣-secretase candidates ADAM10 and TACE, which both are members of the ADAM (a disintegrin and metalloprotease) family. Shedding was analyzed in the presence of the ADAM10 inhibitor GI254023X, or after transfection with small interfering RNAs targeted against TACE. The results clearly demonstrate that different ␣-secretases are involved in IGF-1-induced processing. APP is mainly cleaved by ADAM10, whereas APLP2 processing is mediated by TACE. Finally, we also show that IGF-1 induces PKC-dependent phosphorylation of TACE. Alzheimer disease (AD)2 is histopathologically characterized by the presence of amyloid plaques in the brain parenchyma. The major constituent of the plaques is the amyloid-␤ (A␤) peptide, which is derived from the A␤ precursor protein (APP) by ␤-and ␥-secretase cleavage in the amyloidogenic pathway (1). In addition to A␤, a larger secreted fragment, sAPP␤, and an intracellular fragment (APP intracellular domain) are formed. Proteolytic processing of APP occurs mainly by an alternative pathway. In this nonamyloidogenic pathway, A␤ formation is precluded because ␣-secretase cleaves APP in the middle of the A␤ region. In addition to sAPP␣, a small secreted peptide, p3, and APP intracellular domain are generated by subsequent ␥-secretase cleavage.APP belongs to a conserved gene family including the two mammalian paralogues amyloid precursor-like protein 1 and 2 (APLP1 and APLP2). The exact biological function of APP and its paralogues is still unknown, although several different studies have shown involvement of APP in cell adhesion, neurite outgrowth, synaptogenesis, modulation of synaptic plasticity, and neuroprotection (reviewed in Ref. 2). Homo-and heterotypic cis interactions of APP family members have been detected (3). APLP1 could also form trans interactions, suggesting a specific role of APLP1 in cell adhesion. Importantly, double knock-out studies in mi...

Ezrin/Radixin/Moesin Are Required for the Purinergic P2X7 Receptor (P2X7R)-dependent Processing of the Amyloid Precursor Protein

“…7F), indicating that P2X7R signaling in Neuro2a cells leads to ERM phosphorylation via activation of Rho kinase and MAP kinases, whereas PI3K is downstream of ERM. The involvement of PI3K in the shedding of sAPP␣ was also found when human neuroblastoma SH-SY5Y cells were stimulated with insulin-like growth factor-1 (65,66). In this model, PI3K activity increased the level of ADAM10, which is involved in the non-amyloidogenic processing of APP (66).…”

“…The involvement of PI3K in the shedding of sAPP␣ was also found when human neuroblastoma SH-SY5Y cells were stimulated with insulin-like growth factor-1 (65,66). In this model, PI3K activity increased the level of ADAM10, which is involved in the non-amyloidogenic processing of APP (66). However, we have shown previously that the simultaneous silencing of ADAM9, -10, and -17 does not block the P2X7R-mediated proteolytic processing of APP, indicating that an unidentified ␣-secretase is also triggered by PI3K (4).…”

ADAM10 is overexpressed in human hepatocellular carcinoma and contributes to the proliferation, invasion and migration of HepG2 cells

“…ADAM10 can cleave .05 compared with the blank control group, Lipo2000 group and control siRNA group, respectively). ADAM10, A disintegrin and metalloproteinase 10. several critical transmembrane molecules including amyloid precursor protein (28,29). It must be noted that soluble amyloid precursor protein has been related to the growth of several types of cells (30,31), which suggests that ADAM10 may influence the proliferation of HepG2 cells via amyloid precursor protein shedding.…”

Insulin receptor signaling mediates APP processing and β-amyloid accumulation without altering survival in a transgenic mouse model of Alzheimer’s disease

“…Interestingly, only the α-secretase inhibitor TAPI-2 (Enzo LifeSciences, Lörrach, Germany, 20 μM final concentration) reduced CTF formation whereas the β-secretase inhibitor ( 10 μM final concentration; β-secretase inhibitor II, BioVision Research Products, California, USA) and γ-secretase inhibitor (III-31C, Sigma, 0.2 μM final concentration) had no effect (Fig. 3c) suggesting that endosomal APP procession is mediated mainly via the two possible α-secretases ADAM-10 and/or TACE (Jacobsen et al 2010). However, Western blot analysis of BACE-1, ADAM-10, and TACE did not show any differences between wild-type and siIRS-2 cells (Fig.…”