CNTNAP2 is targeted to endosomes by the polarity protein PAR3

Abstract

A decade of genetic studies has established contactin‐associated protein‐like 2 (CNTNAP2) as a prominent susceptibility gene associated with multiple neurodevelopmental disorders. The development and characterization of Cntnap2 knockout models in multiple species have bolstered this claim by establishing clear connections with certain endophenotypes. Despite these remarkable in vivo findings, CNTNAP2’s molecular functions are relatively unexplored, highlighting the need to identify novel protein partners. Here, we characterized an interaction between CNTNAP2 and partitioning‐defective 3 (PAR3)—a polarity molecule isolated in a yeast two‐hybrid screen with CNTNAP2’s C‐terminus. We provide evidence that the two proteins interact via PDZ domain‐mediated binding, that CNTNAP2+/PAR3+ complexes are largely associated with clathrin‐coated endocytic vesicles in heterologous cells and that PAR3 causes an enlargement of CNTNAP2 puncta size. Live imaging and fluorescence recovery after photobleaching (FRAP) reveals that PAR3 limits the mobility of CNTNAP2. Finally, overexpression of PAR3 but not a PAR3 mutant lacking all PDZ domains (PAR3∆PDZall) can cluster endogenous CNTNAP2 in primary neurons. Collectively, we conclude that PAR3 regulates CNTNAP2 spatial localization.

Shed CNTNAP2 ectodomain is detectable in CSF and regulates Ca2+ homeostasis and network synchrony via PMCA2/ATP2B2

“…A shed ectodomain is a novel extracellular regulator of PMCA2 activity and neuronal Ca 2+ dynamics CNTNAP2 was originally shown to regulate the localization of Shaker-like K + channels on myelinated axons (Poliak et al, 1999(Poliak et al, , 2003. Its intracellular binding partners are reasonably well known (Gao et al, 2018(Gao et al, , 2020Horresh et al, 2008). However, CNTN2 and CNTN1 were the only known partners for its extracellular domain (Poliak et al, 2003;Rubio-Marrero et al, 2016).…”

Altered Expression of Par3, aPKC-λ, and Lgl1 in Hippocampus in Kainic Acid-Induced Status Epilepticus Rat Model

“…Those findings indicated Par3 may display facilitative effort on MFS and may aggravate epileptogenesis. Moreover, Par3 may indirectly contribute to epileptogenesis through CNTNAP2, which has been considered a prominent disease susceptibility gene associated with epilepsy ( 21 , 22 ).…”

“…Previous studies had discovered the long-lasting increased of mRNA expression of PKC epsilon in mossy fiber of adult rats, which followed the seizures induced by kainic acid injection ( 20 ). Moreover, Gao et al also discovered that the PAR3 regulates CNTNAP2 spatial localization ( 21 ). CNTNAP2 has been considered a prominent disease susceptibility gene associated with epilepsy ( 22 ), and seizure was observed in Cntnap2 knockout rat ( 23 ).…”

Assembly and Function of the Juxtaparanodal Kv1 Complex in Health and Disease

“…The selective endocytosis of Caspr2 is achieved in the somato-dendritic compartment based on the PKC-phosphorylation of a short motif in the 4.1B binding region [ 106 ]. Caspr2 can be also targeted to endosomes in dendrites via its C-terminal PDZ-binding domain interacting with PAR3 [ 107 ]. Since PAR3 has been shown to interact with the kinesin Kif3A [ 108 ], Caspr2 may be axonally transported through the Kif3 motor after its somato-dendritic internalization.…”