Cytosolic sensor for calcium, modulates the interaction of STIM1 and ORAI1 upon store depletion and the activation of store-operated Ca(2+) entry (SOCE) and NFAT translocation from cytosol to nucleus (PubMed:30481768). Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating (By similarity). Interacts with STIM1 and ORAI1; the interactions take place upon Ca(2+)-store depletion and dissociate through a Ca(2+)-dependent mechanism. Interaction with STIM1 inhibits STIM1 interaction with SARAF. Truncated N-terminus. Truncated N-terminus.