Espin (ESPN)

Espin (ESPN) is a multifunctional, calcium-insensitive actin-bundling protein encoded by the *ESPN* gene in humans[1][3][5]. Espin is primarily associated with the actin-rich microvillus-type specializations such as stereocilia of sensory hair cells in the inner ear, where it is essential for organizing, elongating, and stabilizing parallel actin bundles[1][3][5]. It plays a crucial role in sensory transduction for hearing and balance, and mutations in ESPN disrupt stereocilia structure—causing autosomal recessive (DFNB36) and autosomal dominant non-syndromic sensorineural deafness in humans, and similar defects in mice (jerker phenotype)[1][3][5]. Espin activity depends on multiple interaction domains, including a unique WH2 domain facilitating targeted actin bundle assembly, and is regulated by binding partners like class III myosins[3]. There are no currently approved drugs targeting espin, and it is not considered a clinical therapeutic target. It functions as an essential cytoskeletal structural protein rather than a receptor, enzyme, or canonical drug target[1][3][5].

Other names

DFNB36LP2654Autosomal recessive deafness type 36 proteinEctoplasmic specialization proteinUSH1Mespinectoplasmic specialization protein