EF-hand domain-containing family member B (EFHB)

EF-hand domain-containing family member B (EFHB, also known as CFAP21) is a protein in humans encoded by the EFHB gene located on chromosome 3. It contains two EF-hand motifs at its C-terminus, which are calcium-binding domains commonly found in proteins involved in calcium signaling[7]. EFHB acts as a microtubule inner protein present in the doublet microtubules of cilia and flagella, where it is required for proper motile cilia beating[3][6]. EFHB also plays a role as a calcium ion sensor, regulating store-operated Ca²⁺ entry (SOCE) through interaction with other proteins such as STIM1 and ORAI1, and modulating the calcineurin-NFAT signaling pathway[1][4][5][6]. While highly associated with ciliary and flagellar structure and function, and broadly expressed in human tissues, EFHB is not currently recognized as a classic therapeutic target, and there are no approved drugs or known direct safety concerns related to it. Its gene has, however, been studied in various expression and knockout phenotyping studies, suggesting an association with ciliary biology and possibly with related rare diseases, but no firm disease link or actionable biomarker role is established at present[1][5][6].

Other names

CFAP21FLJ25200Cilia- and flagella-associated protein 21cilia and flagella associated protein 21