The Slitrk family comprises six vertebrate members (Slitrk1-6) that are highly expressed in the central nervous system (CNS), where they modulate neurite outgrowth. In humans, Slitrk1-6 are neuronal transmembrane proteins and are key synapse organizers at neuronal synapses through interactions with specific members of the presynaptic type IIa receptor protein tyrosine phosphatase (RPTP) family []. They contain two consecutive extracellular LRR modules, LRR1 and LRR2, and a single transmembrane domain, followed by an intracellular domain that is homologous to Trks. Mutations in human SLITRKs have been implicated in several neuropsychiatric disorders, including Tourette's syndrome, schizophrenia, trichotillomania and obsessive-compulsive disorder (OCD) []. Slitrk1 and Slitrk2 have been shown to regulate synapse formation between hippocampal neurons [].
Receptor-type tyrosine-protein phosphatase delta (R-PTP-delta, also known as PTPRD), belongs to the LAR (leukocyte common antigen-related) family of receptor-type tyrosine-protein phosphatases (RPTPs), which belong to the larger family of classical tyrosine-specific protein tyrosine phosphatases (PTPs). PTPs () catalyze the dephosphorylation of phosphotyrosine peptides. LAR-RPTPs are synaptic adhesion molecules that play roles in various aspects of neuronal development, including axon guidance, neurite extension, and synapse formation and function [, , ]. PTPRD is involved in pre-synaptic differentiation through interaction with SLITRK2 [, ]. It contains an extracellular region with three immunoglobulin-like (Ig) domains and four to eight fibronectin type III (FN3) repeats (determined by alternative splicing), a single transmembrane domain, followed by an intracellular region with a membrane-proximal catalytic PTP domain (repeat 1, also called D1) and a membrane-distal non-catalytic PTP-like domain (repeat 2, also called D2) [, , ].This entry represents the catalytic PTP domain (repeat 1) found in the protein PTPRD from chordates.
