Binds to membranes via its F-BAR domain and mediates membrane tubulation. Plays a role in the reorganization of the microtubule cytoskeleton via its interaction with MAPT; this decreases microtubule stability and inhibits MAPT-induced microtubule polymerization. Plays a role in cellular transport processes by recruiting DNM1, DNM2 and DNM3 to membranes. Plays a role in the reorganization of the actin cytoskeleton and in neuron morphogenesis via its interaction with COBL and WASL, and by recruiting COBL to the cell cortex. Plays a role in the regulation of neurite formation, neurite branching and the regulation of neurite length. Required for normal synaptic vesicle endocytosis; this process retrieves previously released neurotransmitters to accommodate multiple cycles of neurotransmission. Required for normal excitatory and inhibitory synaptic transmission. Homodimer. May form heterooligomers with other PACSINs. Interacts with both COBL and DBNL. Identified in a complex composed of COBL, PACSIN1 and WASL. Interacts with EHD3 (By similarity). Interacts (via SH3 domain) with SYNJ1 and WASL. Interacts (via SH3 domain) with DNM1; the interaction is reduced by DNM1 phosphorylation. Interacts with DNM2 and DNM3. Interacts with MAPT. Interacts with EHD1. Interacts with TRPV4. In primary neuronal cultures, present at a high level in presynaptic nerve terminals and in the cell body. Colocalizes with DNM1 at vesicular structures in the cell body and neurites (By similarity). Colocalizes with MAPT in axons. Highly expressed in brain. Detected in hippocampus and dorsal root ganglion neurons. Detected in rod photoreceptor terminals in the outer plexiform layer of the retina (at protein level). In CNS neurons, high levels in the pyramidal cells of the hippocampus, Purkinje cells of the cerebellum and large neurons of the cortex and brain stem. Expression is seen at embryonic day 17 and is up-regulated developmentally with a correlation to neuronal differentiation. The F-BAR domain forms a coiled coil and mediates membrane-binding and membrane tubulation. In the autoinhibited conformation, interaction with the SH3 domain inhibits membrane tubulation mediated by the F-BAR domain. DNM1 binding abolishes autoinhibition. Phosphorylated by casein kinase 2 (CK2) and protein kinase C (PKC). Mice are born at the expected Mendelian rate, but display a slightly reduced body weight and reduced fertility. Mice display increased synaptic vesicle diameter and impaired compensatory synaptic vesicle endocytosis after high synapse activity. Rod photoreceptor ribbon synapses display an abnormally high number of endosome-like structures and tubular elements after light exposure. Mice display defects in excitatory and inhibitory synaptic transmission in the hippocampus, and display a tendency to seizures when confronted with novelty. Belongs to the PACSIN family.