Retinoic acid-induced upregulation of the metalloendopeptidase nardilysin is accelerated by co-expression of the brain-specific protein p42IP4 (centaurin α1; ADAP1) in neuroblastoma cells

The mainly neuronally expressed protein p42IP4 (centaurin α1; ADAP1), which interacts with the metalloendopeptidase nardilysin (NRD) was found to be localized in neuritic plaques in Alzheimer disease (AD) brains. NRD was shown to enhance the cleavage of the amyloid precursor protein (APP) by α-secretases, thereby increasing the release of neuroprotective sAPPα. We here investigated in vitro the biochemical interaction of p42IP4 and NRD and studied the physiological interaction in SH-SY5Y cells. NRD is a member of the M16 family of metalloendopeptidases. Some members of this M16 family act bi-functionally, as protease and as non-enzymatic scaffold protein. Here, we show that p42IP4 enhances the enzymatic activity of NRD 3–4 times. However, p42IP4 is not a substrate for NRD. Furthermore, we report that differentiation of SH-SY5Y cells by stimulation with 10 μM retinoic acid (RA) results in upregulation of NRD protein levels, with a 6-fold rise after 15 days. NRD is expressed in the neurites of RA-stimulated SH-SY5Y cells, and localized in vesicular structures. Since p42IP4 is not expressed in untreated SH-SY5Y cells, we could use this cell system as a model to find out, whether there is a functional interaction. Interestingly, SH-SY5Y cells, which we stably transfected with GFP-tagged-p42IP4 showed an enhanced NRD protein expression already at an earlier time point after RA stimulation.

► Neuronal protein p42IP4 is no substrate of metalloendopeptidase nardilysin.
► p42IP4 (centaurin α1/ADAP1) enhances enzymatic peptidase activity of nardilysin.
► Nardilysin level in SH-SY5Y cells is upregulated after retinoic acid treatment.
► Expression of p42IP4 accelerates kinetics of upregulation of nardilysin.
► No influence or involvement of p42IP4 in amyloid precursor protein shedding.