RT Journal Article SR Electronic T1 The CPPDD-Associated ANKH M48T Mutation Interrupts the Interaction of ANKH with the Sodium/Phosphate Cotransporter PiT-1 JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP jrheum.081118 DO 10.3899/jrheum.081118 A1 John Wang A1 Hing Wo Tsui A1 Frank Beier A1 Florence W.L. Tsui YR 2009 UL http://www.jrheum.org/content/early/2009/04/14/jrheum.081118.abstract AB Objective Numerous dominant human homolog of progressive ankylosis (ANKH) mutations have been identified in familial calcium pyrophosphate dihydrate crystal deposition disease (CPPDD). Due to the dominant nature of these mutations, we investigated whether ANKH interacts with other proteins; and if so, whether any CPPDD-associated ANKH mutation might disrupt such protein interactions. Methods Stable ATDC5 ANKH wt- and ANKH M48T-transfectants were generated. Lysates from these transfectants were used to identify candidate protein interaction with ANKH by coimmunoprecipitation followed by Western blot analysis. The effect of high phosphate on the expression of genes involved in modulating Pi (inorganic phosphate)/PPi (inorganic pyrophosphate) homeostasis in these transfectants was assessed. Results We showed that ANKH protein associates with the sodium/phosphate cotransporter PiT-1, and that ANKH M48T mutant protein failed to interact with PiT-1. We also showed that upon high phosphate treatment, the normally coordinated upregulation of endogenous Ank and PiT1 transcript expression was disrupted in ANKH M48T transfectants. Conclusion Our results suggested that there is a coordinated interrelationship between 2 key participants of Pi and PPi metabolism, ANKH and PiT-1.