Changes in spectrin, striatal-enriched tyrosine phosphatase (STEP), PTPN13 breakdown product (P13BP), and TAR DNA-binding protein of about 43 kDa (TDP-43) in brain of WT, calpain-1 knock out (C1KO), and C2CKO mice 24 h after traumatic brain injury (TBI). (A,B) Representative western blots (WBs) of ipsilateral cortical tissue (P2 fraction) from WT, C1KO, and C2CKO mice collected 24 h after TBI or sham surgery. Note that calpain-1 is absent in C1KO mice and calpain-2 levels were reduced in C2CKO mice. Several calpain substrates including spectrin (1:500; MAB1622, EMD Millipore, Burlington, MA, USA), STEP (1:1000, NB300-202, Novus Biologicals, Colorado, CO, USA), PTPN13 (1:1000, PA5-72906, Thermo Fisher Scientific, Waltham, MA, USA), and TDP-43 (1:1000, 10782-2-AP, Proteintech, Chicago, IL, USA) were probed, and their fragments generated by calpain cleavage including SBDP, STEP33, and P13BPs were detected after TBI. (C) Quantification of WB. Ratios of SBDPs to spectrin, STEP33 to STEP61, P13BPs to PTPN13 were significantly increased in WT and C1KO but not in C2CKO mice after TBI. Levels of TDP-43 were not changed after TBI in all genotypes. * p < 0.05, ** p < 0.01. ns, no significant difference. N = 4. One way ANOVA followed by Bonferroni’s test. Full immunoblots for the blots shown here are presented in the Supplementary Materials.