Shedding of the amyloid precursor protein‐like protein APLP2 by disintegrin‐metalloproteinases

Abstract

The amyloid precursor protein (APP) is a member of a protein family in mammals that includes the APP-like proteins APLP1 and APLP2 [1]. All APP ⁄ APLP family members are type I integral membrane proteins with large extracellular ectodomains and short cytoplasmic tails. Compared with APP, both APLPs are highly homologous in their amino acid sequence (e.g. APLP2 ⁄ APP 52% identical, 71% similar) [2] and are proteolytically processed in a similar way. The N-terminal ectodomains are released by a shedding enzyme [2,3], whereas the C-termini remain in the membrane [2,4,5] and can be further processed to release a cytoplasmic fragment with signaling properties [4,6,7].Further elucidation of APLP2-processing is of relevance with regard to the outstanding function of this protein, which was derived from knockout experiments. Whereas a double knockout of APP and APLP1 did not show severe phenotypic changes in mice, the combined knockout of APLP2 with both of the other APP family members resulted in postnatal lethality [8,9]. This shows that APLP2 and ⁄ or one of its proteolytic fragments are essential for normal development and Cleavage of the amyloid precursor protein (APP) within the amyloid-beta (Ab) sequence by the a-secretase prevents the formation of toxic Ab peptides. It has been shown that the disintegrin-metalloproteinases ADAM10 and TACE (ADAM17) act as a-secretases and stimulate the generation of a soluble neuroprotective fragment of APP, APPsa. Here we demonstrate that the related APP-like protein 2 (APLP2), which has been shown to be essential for development and survival of mice, is also a substrate for both proteinases. Overexpression of either ADAM10 or TACE in HEK293 cells increased the release of neurotrophic soluble APLP2 severalfold. The strongest inhibition of APLP2 shedding in neuroblastoma cells was observed with an ADAM10-preferring inhibitor. Transgenic mice with neuron-specific overexpression of ADAM10 showed significantly increased levels of soluble APLP2 and its C-terminal fragments. To elucidate a possible regulatory mechanism of APLP2 shedding in the neuronal context, we examined retinoic acid-induced differentiation of neuroblastoma cells. Retinoic acid treatment of two neuroblastoma cell lines upregulated the expression of both APLP2 and ADAM10, thus leading to an increased release of soluble APLP2.Abbreviations ADAM, a disintegrin and metalloproteinase; ADAM10DN, catalytically inactive dominant negative mutant form of ADAM10; APLP1, APP-like protein 1; APLP2, APP-like protein 2; APLP2s, cleaved soluble APLP2; APP, amyloid precursor protein; BACE, b-site APP-cleaving enzyme; CS-GAG, chondroitin sulfate glycosaminoglycan; PKC, protein kinase C; PMA, phorbol-12-myristate-13-acetate; PVDF, poly(vinylidene difluoride); RA, retinoic acid; TACE, tumor necrosis factor-a converting enzyme.

Phorbol Ester-induced Shedding of the Prostate Cancer Marker Transmembrane Protein with Epidermal Growth Factor and Two Follistatin Motifs 2 Is Mediated by the Disintegrin and Metalloproteinase-17

“…2E, lanes 3 and 6). An increase in full-length TMEFF2 in cell lysates was not apparent by Western blot analysis (not shown), which is in good agreement with published data with other proteins such as the amyloid precursor protein-like protein (APLP2) (51). This reflects that only cell surface protein is cleaved from the cell membrane, representing a fraction of the total protein.…”

Intracellular domains of amyloid precursor-like protein 2 interact with CP2 transcription factor in the nucleus and induce glycogen synthase kinase-3β expression

“…26,27 APP, which is a type I transmembrane protein as well as APLPs, is cleaved consecutively, first at the extracellular juxtamembrane region by a-or b-secretase and secondly at the intramembrane region by g-secretase. 26 Similarly with APP, the N-terminal ectodomain of APLP2 is shedded by b-secretase 28,29 as well as by ADAM 10 and 17, 30 whereas the C-termini remain in the membrane 10,28 and can be further processed by g-or e-secretases 13,14 to release ICDs with signaling properties. 10,28 The APLP2-ICDs are known to interact with Fe65 via a YENPTY domain, which APP, APLP1 and APLP2 have in common in their C-terminus, translocating into the nucleus by Fe65-dependent manner 8 and show Fe65-dependent gene transcriptional activity by heterologous reporter genes.…”

Physiological Functions of APP Family Proteins

“…Likewise, p3/ Ab-like fragments (Eggert et al 2004;Minogue et al 2009), as well as APLP1 and APLP2 intracellular fragments (termed ALIDs) are generated in a g-secretase dependent manner (Scheinfeld et al 2002;Walsh et al 2003). Whereas there has been robust evidence indicating that APLP2 is processed by a-and b-secretase (Eggert et al 2004;Pastorino et al 2004;Endres et al 2005), APLP1 shedding appeared to be independent of BACE activity as it was not affected by BACE inhibitors (Eggert et al 2004;Minogue et al 2009). A recent study using BACE-KO and overexpressing mice showed, however, that BACE deficiency substantially reduces brain APLP1s levels and that ICDs of APP family members are released in the absence of BACE (Frigerio et al 2010).…”