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 (By similarity). Binds to membranes via its F-BAR domain and mediates membrane tubulation. May form heterooligomers with other PACSINs. Interacts with MAPT. Interacts with TRPV4 (By similarity). Interacts (via SH3 domain) with SYNJ1 and WASL. Interacts with DNM2 and DNM3. Interacts with both COBL and DBNL. Identified in a complex composed of COBL, PACSIN1 and WASL. Interacts with EHD1 and EHD3 (By similarity). Homodimer. Interacts (via SH3 domain) with DNM1; the interaction is reduced by DNM1 phosphorylation. Colocalizes with MAPT in axons. 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). Associates with membranes via its F-BAR domain. Highly expressed in brain and, at much lower levels, in heart and pancreas. 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 (By similarity). Phosphorylated by casein kinase 2 (CK2) and protein kinase C (PKC). Belongs to the PACSIN family. Extended N-terminus.