Mechanical function and Biophysical Properties of the REJ region of Polycystin-1

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Mutations of Polycystin-1 (PC1) account for 85% Autosomal dominant polycystic kidney disease (ADPKD), which is the most common life-threatening inherited disease worldwide. PC1 has been implicated to be involved in renal tubule and kidney morphogenesis as a mechanosensor and transduce the signals into cellular response. Most domains of the long PC1's ectodomain of are mechanical stable Ig-like motifs and may function as effective force transmitters to regulate the multi-function properties of PC1. The REJ region is a major component of PC1s ectodomain (30% or ∼1000 aa); however its structure and function remains unknown. Here we used protein engineering in combination with single-molecule AFM and circular dichroism (CD) techniques to elucidate the structure and mechanical properties of this region. Our studies indicates that the REJ region has complex mechanical properties. Stretching a protein construct which includes four PKD Ig-like domains and the complete REJ region, resulted in saw-tooth patterns with 3-10 force peaks with a wide range of unfolding forces of 50-250 pN, suggesting that the extra force peaks must originate from the REJ region. We also made several REJ constructs (I27)3-REJ FN4-(I27)2 and (I27)3-REJ FN3,4-(I27)2 and expressed them in bacteria and insect cells. Stretching these constructs generated peaks characteristic of the unfolding of titin I27 as well as other more complex unfolding events which we attribute to the unfolding of REJ domains. The complexity of the REJ domain unfolding force patterns suggests that these domains may have unfolding intermediates. These results support the hypothesis that PC1 is a mechano-transducer with a novel molecular architecture and elastic properties well-suited for sensing and transmitting distinct mechanical signals with a wide range of strengths.




Xu, M., Ma, L., Odunuga, OO., Delgardo, E., & Oberhauser, A (2009), Mechanical function and biophysical properties of the REJ region of polycystin -1. Biophysical Journal 96(3):641a.




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