Calsyntenins Mediate TGN Exit of APP in a Kinesin‐1‐Dependent Manner

Abstract

Kinesin motors are required for the export of membranous cargo from the trans-Golgi network (TGN), yet information about how kinesins are recruited to forming transport intermediates is sparse. Here we show that the Kinesin-1 docking protein calsyntenin-1 localizes to the TGN in vivo and directly and specifically recruits Kinesin-1 to Golgi/TGN membranes as well as to dynamic post-Golgi carriers. Overexpression of various calsyntenin chimeras and kinesin light chain 1 (KLC1) at high levels caused the formation of aberrant membrane stacks at the endoplasmic reticulum (ER) or the Golgi, disrupted overall Golgi structure and blocked exit of calsyntenin from the TGN. Intriguingly, this blockade of calsyntenin exit strongly and selectively impeded TGN exit of amyloid precursor protein (APP). Using live cell microscopy we found that calsyntenins exit the TGN in Kinesin-1-decorated tubular structures which may serve as carriers for calsyntenin-1-mediated post-TGN transport of APP. Abrogation of this pathway via virus-mediated knockdown of calsyntenin-1 expression in primary cultured neurons caused a marked elevation of APP C-terminal fragments. Together, these results indicate a role for calsyntenin-1 in Kinesin-1-dependent TGN exit and postGolgi transport of APP-containing organelles and further suggest that distinct intracellular routes may exhibit different capacities for proteolytic processing of APP.

Targeting NMNAT1 to Axons and Synapses Transforms Its Neuroprotective PotencyIn Vivo

“…Calsyntenin-1 is a neuronal transmembrane protein transported to axons in vesicular carriers in a kinesin 1-dependent manner (Konecna et al, 2006;Ludwig et al, 2009). Strikingly, by using the same subcellular fraction method that we use in the present study, Ludwig et al (2009) showed that calsyntenin-1 concentrates in the subcellular vesicle fractions V0 and V1, where we found Ax-NMNAT1 and Wld S mostly present. Although we show that Ax-NMNAT1 does not colocalize with calsyntenin-1, and p38 SNPH, we cannot exclude a possible colocalization with other vesicles of similar size.…”

“…The exit of neurexin from the ER/Golgi and its trafficking to synapses in vesicles depends on its C-terminal sequence, where the domain for interaction with Mint1 resides (Fairless et al, 2008). Although a direct interaction between APP and kinesin is controversial (Kamal et al, 2001;Lazarov et al, 2005), the exit of vesicles containing APP from the trans-Golgi-network is mediated by calsyntenin-1 (Ludwig et al, 2009). Calsyntenin-1 is a neuronal transmembrane protein transported to axons in vesicular carriers in a kinesin 1-dependent manner (Konecna et al, 2006;Ludwig et al, 2009).…”

“…Although a direct interaction between APP and kinesin is controversial (Kamal et al, 2001;Lazarov et al, 2005), the exit of vesicles containing APP from the trans-Golgi-network is mediated by calsyntenin-1 (Ludwig et al, 2009). Calsyntenin-1 is a neuronal transmembrane protein transported to axons in vesicular carriers in a kinesin 1-dependent manner (Konecna et al, 2006;Ludwig et al, 2009). Strikingly, by using the same subcellular fraction method that we use in the present study, Ludwig et al (2009) showed that calsyntenin-1 concentrates in the subcellular vesicle fractions V0 and V1, where we found Ax-NMNAT1 and Wld S mostly present.…”

Phosphorylation of kinesin light chain 1 at serine 460 modulates binding and trafficking of calsyntenin-1

“…Calsyntenin-1 is widely expressed but is particularly abundant in the nervous system, where it is present in most neuronal subtypes (Hintsch et al, 2002). As a direct binding partner for KLC1, calsyntenin-1 has been implicated in the transport of a subset of vesicles and especially vesicles undergoing transport through axons of neurons (Araki et al, 2007;Konecna et al, 2006;Ludwig et al, 2009).…”

Cytoplasmic Fragment of Alcadein α Generated by Regulated Intramembrane Proteolysis Enhances Amyloid β-Protein Precursor (APP) Transport into the Late Secretory Pathway and Facilitates APP Cleavage

“…Alc␣/ calsyntenin-1 is also subject to intracellular trafficking and metabolism and participates in neural functions, similar to APP (4, 9 -11). Calsyntenins have also been reported to mediate exit of APP from the TGN (12).…”