The noncatalytic TrkCNC2 receptor is cleaved by metalloproteases upon neurotrophin-3 stimulation

Abstract

The trkC locus encodes catalytic and noncatalytic receptors, generated by alternative splicing. These primary high-affinity neurotrophin-3 (NT-3) receptors may act in concert to modulate responsiveness to NT-3. Signal modulation can also be achieved by receptors that are post-translationally processed. We report that the noncatalytic TrkC receptor, TrkCNC2, is cleaved at the membrane-proximal region of its extracellular domain. This generates a soluble ectodomain (gp90 TrkCNC2 ) recovered in the cell culture medium and a membrane-bound fragment (p20 TrkCNC2 ), which contains the transmembrane and intracellular regions including the juxtamembrane and the NC2-specific cytoplasmic domains. We also show that this processing, which does not occur in the TrkC catalytic counterpart, is upregulated by NT-3 and upon treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. Moreover, cleavage inhibition after EDTA or 1.10 phenanthroline treatment suggests involvement of a metalloprotease(s). Finally, this post-translational processing was observed not only in TrkCNC2-overexpressing NIH3T3 cells but also in primary cultures of cortical neurons and brain extracts. This study shows that, in addition to alternative splicing, ectodomain shedding represents a novel means of regulating TrkC receptor signaling, and consequently NT-3 biological effects on target cells.

Axonal transport and neuronal transcytosis of trophic factors, tracers, and pathogens

“…Based on recent studies in other cell types, one might envision that MVBs could fuse with the neuronal plasma membrane, which could result in the release of their vesicular content as shown for "exosome" release (Denzer et al, 2000), but in neurons there is no evidence yet for such a release mechanism. Consistent with the concept of receptor cleavage, ectodomain shedding appears to be relatively common, as it has been reported for several trophic receptors, including the p75 neurotrophin receptor (DiStefano and Johnson, 1988;Kanning et al, 2003), truncated Trk receptor (Mateos et al, 2003), receptors for tumor necrosis factor (TNF, Kohno et al, 1990), EGF (Murthy et al, 1987), IGF-I (Burgess et al, 1987), PDGF (Tiesman and Hart, 1993), FGFs (Hanneken et al, 1994), hepatocyte growth factor/scatter factor (HGF/SF, Prat et al, 1991), and GDNF (GFRalpha1, Worley et al, 2000;Airaksinen and Saarma, 2002). Several of these receptors bind ligands that are known to be transcytosed in neurons (neurotrophins, bFGF, IGF-I, GDNF) or in other cell types (EGF) (for recent reviews, see Table 1 or von .…”

Metzincin Proteases and Their Inhibitors: Foes or Friends in Nervous System Physiology?

“…In keeping with their role in physiological as well as pathological tissue remodeling (Yong, 2005; Page-McCaw et al, 2007; Agrawal et al, 2008; Rosenberg, 2009a), MMP expression is regulated at the level of transcription by a variety of growth factors, cytokines, and chemokines, though post-transcriptional and epigenetic modification may also contribute (Clark et al, 2007). It is now well accepted that MMPs not only degrade extracellular matrix (ECM) proteins of relevance to nervous system physiology (e.g., laminin, the chondroitin sulfate proteoglycan (CSPG) brevican, and the glycoprotein tenascin-R), but also activate growth factors (e.g., proNGF and proBDNF) and their receptors (e.g., trkA, trkC and p75), cytokines (e.g., proTNF-α, proIL-1β), and “shed” ECM receptors (e.g., N-cadherin, β-dystroglycan, and Ephrin-B2) (Schönbeck et al, 1998; Diaz-Rodriguez et al, 1999; McCawley and Matrisian, 2001; Jung et al, 2003; Mateos et al, 2003; Bruno and Cuello, 2006; Ethell and Ethell, 2007; Michaluk et al, 2007; Rodríguez et al, 2010). Because MMP-2, MMP-3, and MMP-9 are the most abundantly expressed MMPs within the brain, antibody reagents are readily available, and MMP-2 and MMP-9 can be easily identified by gelatin zymography, their role in the nervous system has been best characterized.…”

Stable expression of intracellular Notch suppresses v-Src-induced transformation in avian neural cells

“…Cell lysates preparation, protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Westernblotting were performed as described previously (Mateos et al, 2003). Blots were probed with primary antibodies used at the following dilutions: anti-T7 epitope monoclonal antibody Sheep anti-mouse secondary antibody conjugated to horseradish peroxidase (Amersham Pharmacia Biotech) diluted to 1:10 000 was used for monoclonal antibodies.…”