Enables protein homodimerization activity. Involved in establishment of protein localization to plasma membrane and homophilic cell adhesion via plasma membrane adhesion molecules. Acts upstream of or within several processes, including camera-type eye morphogenesis; fertilization; and protein localization to cell junction. Located in several cellular components, including adherens junction; apical junction complex; and cell-cell contact zone. Is integral component of postsynaptic density membrane. Is active in hippocampal mossy fiber to CA3 synapse. Is expressed in several structures, including nervous system; sensory organ; skeletal musculature; tooth; and vibrissa. Orthologous to human NECTIN3 (nectin cell adhesion molecule 3). [provided by Alliance of Genome Resources, Apr 2022]