Interactome based identification and validation of prefoldin 5-α for prognosing CNS leukemia in B-ALL patients.

We report here the identification and validation of prefoldin 5-alpha (PFDN5-α) for the first time as prognostic biomarker for prediction of central nervous system (CNS) leukemia of B cell acute lymphoblastic leukemia (B-ALL) origin. Since cerebrospinal fluid (CSF) cytology being the gold standard of diagnosis for CNS leukemia with poor sensitivity, mandatory prophylactic intrathecal chemotherapy is administered irrespective of patients develop CNS leukemia. Thus, using interactome studies, we identified PFDN5-α as a prognostic biomarker for predicting CNS leukemia by interacting lymphoblastic proteins and CSF from B-ALL patients using far-western clinical proteomics approach. Validation by both western and ELISA methods confirmed our results. For further clinical translation, we performed Receiver Operating Characteristic (ROC) curve analysis generated from CNS +ve (n = 25) and -ve (n = 40) CSF samples from B-ALL patients and identified PFDN5-α-CSF reactivity cut-off value as 0.456. Values below 0.456 indicate the patient is at risk of developing CNS leukemia and suggestive of having intrathecal chemotherapy. Further flow cytometry validation for CNS leukemia positivity revealed that with increasing blast cells, a decrease in PFDN5-α-CSF reactivity confirming ELISA based PFDN5α-CSF reactivity assay. Predicting CNS leukemia development risk by ELISA based PFDN5-α-CSF reactivity assay could have potential in the clinical management of CNS leukemia.

Distinct actin-dependent nanoscale assemblies underlie the dynamic and hierarchical organization of E-cadherin.

Cadherins are transmembrane adhesion proteins required for the formation of cohesive tissues.1-4 Intracellular interactions of E-cadherin with the Catenin family proteins, α- and ß-catenin, facilitate connections with the cortical actomyosin network. This is necessary for maintaining the integrity of cell-cell adhesion in epithelial tissues.5-11 The supra-molecular architecture of E-cadherin is an important feature of its adhesion function; cis and trans interactions of E-cadherin are deployed12-15 to form clusters, both in cis and trans.11,16-21 Studies in Drosophila embryo have also shown that Drosophila E-cadherin (dE-cad) is organized as finite-sized dynamic clusters that localize with actin patches at cell-cell junctions, in continuous exchange with the extra-junctional pool of dE-cad surrounding the clusters.11,19 Here, we use the ectopic expression of dE-cad in larval hemocytes, which lack endogenous dE-cad to recapitulate functional cell-cell junctions in a convenient model system. We find that, while dE-cad at cell-cell junctions in hemocytes exhibits a clustered trans-paired organization similar to that reported previously in embryonic epithelial tissue, extra-junctional dE-cad is also organized as relatively immobile nanoclusters as well as more loosely packed diffusive oligomers. Oligomers are promoted by cis interactions of the ectodomain, and their growth is counteracted by the activity of cortical actomyosin. Oligomers in turn promote assembly of dense nanoclusters that require cortical actomyosin activity. Thus, cortical actin activity remodels oligomers and generates nanoclusters. The requirement for dynamic actin in the organization of dE-cad at the nanoscale may provide a mechanism to dynamically tune junctional strength.