Sidekick cell adhesion molecule 1 (SDK1)

Sidekick cell adhesion molecule 1 is a large, single-pass transmembrane protein with six N-terminal immunoglobulin-like domains and thirteen fibronectin type III domains, plus an intracellular PDZ-binding motif for complex formation at synaptic sites[1][2][3][5]. SDK1 mediates homophilic binding (SDK1 binds SDK1 on neighboring cells) and is critical for specifying connections between certain types of neurons, especially in the retina, where it shapes the assembly of synaptic circuits by restricting synapse formation to precise cell layers[3][4][5]. Although SDK1’s role in synaptic specificity is well documented, there are currently no drugs targeting SDK1 or its pathways, nor is it established as a standard biomarker or therapeutic target[1][2][3][5]. SDK1 is composed of 2,213 amino acids, with a signal sequence, six immunoglobulin domains, thirteen fibronectin type III domains, a transmembrane region, and a cytoplasmic tail that binds PDZ-domain scaffolding proteins for synaptic localization[2][3][5]. Homophilic cell adhesion mediated by SDK1 is responsible for neuronal targeting specificity; the four N-terminal Ig domains adopt a horseshoe conformation mediating binding[2][3][5]. The gene undergoes alternative splicing, with poorly characterized isoform-specific functions[1][3]. SDK1 is a structurally and functionally validated neuronal cell adhesion molecule of the immunoglobulin superfamily, but has not yet transitioned into clinical targeting for therapeutic intervention or biomarker development[1][2][3][5].

Other names

SDK1Sidekick-1FLJ31425sidekick homolog 1protein sidekick-1cell adhesion molecule SDK1