PTPσ functions as a presynaptic receptor for the glypican-4/LRRTM4 complex and is essential for excitatory synaptic transmission
Authors
Ji Seung Ko ; Gopal Pramanik ; Ji Won Um ; Ji Seon Shim ; Dongmin Lee ; Kee Hun Kim ; Gug-Young Chung ; Giuseppe Condomitti ; Ho Min Kim ; Hyun Kim ; Joris de Wit ; Kang-Sik Park ; Katsuhiko Tabuchi ; Jaewon Ko
Citation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol.112(6) : 1874-1879, 2015
Leukocyte common antigen-related receptor protein tyrosine phosphatases--comprising LAR, PTPδ, and PTPσ--are synaptic adhesion molecules that organize synapse development. Here, we identify glypican 4 (GPC-4) as a ligand for PTPσ. GPC-4 showed strong (nanomolar) affinity and heparan sulfate (HS)-dependent interaction with the Ig domains of PTPσ. PTPσ bound only to proteolytically cleaved GPC-4 and formed additional complex with leucine-rich repeat transmembrane protein 4 (LRRTM4) in rat brains. Moreover, single knockdown (KD) of PTPσ, but not LAR, in cultured neurons significantly reduced the synaptogenic activity of LRRTM4, a postsynaptic ligand of GPC-4, in heterologous synapse-formation assays. Finally, PTPσ KD dramatically decreased both the frequency and amplitude of excitatory synaptic transmission. This effect was reversed by wild-type PTPσ, but not by a HS-binding-defective PTPσ mutant. Our results collectively suggest that presynaptic PTPσ, together with GPC-4, acts in a HS-dependent manner to maintain excitatory synapse development and function.