PGRN processing promotes neuronal outgrowth and branching. (A) Time course analysis of rPGRN subjected to elastase digest. PGRN cleavage products visualized by SDS-PAGE, post-stain with sypro ruby solution (Sigma). Note that the co-treatment of recombinant SLPI blocks elastase-mediated rPGRN cleavage. (B,C) Bar graphs depict quantification of total neurite outgrowth (B) and branching (C) of WT and Grn−/− neurons treated with or without rSLPI. Note that in these experiments no rPGRN was added, therefore rSLPI blocks endogenous Pgrn. (D) Schematic representation of recombinant proteins analyzed in primary hippocampal neurons. (E) WT hippocampal cultures treated with recombinant granulin E (rGRN E) and granulin C (rGRN C) promote outgrowth similar to full length PGRN Data is presented as the mean ± SEM. *p < 0.05; ***p < 0.001.