Modulation of TMEM16B channel activity by the calcium-activated chloride channel regulator 4 (CLCA4) in human cells

The Ca²⁺-activated Cl^- channel regulator CLCA1 potentiates the activity of the Ca²⁺-activated Cl^- channel (CaCC) TMEM16A by directly engaging the channel at the cell surface, inhibiting its reinternalization and increasing Ca²⁺-dependent Cl^- current (I_CaCC) density. We now present evidence of functional pairing between two other CLCA and TMEM16 protein family members, namely CLCA4 and the CaCC TMEM16B. Similar to CLCA1, (i) CLCA4 is a self-cleaving metalloprotease, and the N-terminal portion (N-CLCA4) is secreted; (ii) the von Willebrand factor type A (VWA) domain in N-CLCA4 is sufficient to potentiate I_CaCC in HEK293T cells; and (iii) this is mediated by the metal ion-dependent adhesion site motif within VWA. The results indicate that, despite the conserved regulatory mechanism and homology between CLCA1 and CLCA4, CLCA4-dependent I_CaCC are carried by TMEM16B, rather than TMEM16A. Our findings show specificity in CLCA/TMEM16 interactions and suggest broad physiological and pathophysiological links between these two protein families.