Regulates the dendritic spine distribution of CTTN/cortactin in hippocampal neurons, and thus controls dendritic spinogenesis and dendritic spine maintenance. Interacts with CTTN/cortactin SH3 domain. Interacts with STRN, STRN4/zinedin and MOB4/phocein; this interaction may regulate dendritic spine distribution of STRN and STRN4 in hippocampal neurons (By similarity). Activation of glutamate receptors weakens the interaction with STRN and STRN4 (By similarity). Remains associated with dendritic spines even after glutamate stimulation. Isoform 2 is predominantly expressed in brain (at protein level). In the brain, expressed at high levels in hypothalamus and striatum and at lower levels in cerebellum and cortex. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Due to intron retention. May be due to competing acceptor splice site. Erroneous CDS prediction and frameshift.