Dataset 1: Raw data supporting the findings presented in this study.

The raw data shows full size film images of probed membranes. Full size membranes resulting from transfer of full size gels were often vertically cut to separate replicate sets of samples typically separated by MR markers for simultaneous probing of the different membrane fragments with different antibodies. For optimal resolution of the α11.2 long and short forms, which exhibit high MR, gels were run until the 60 kDa MR marker was either close to the very bottom of the gel or completely run off. Raw data for Figure 2. Determination of antibody specificity for α11.2 with conditional α11.2 KO mice. Original source images for Figure 2: (A) Immunoblots of Triton X-100 extracts from conditional α11.2 KO mice (KO) and litter matched WT mice using gels polymerized from 8% acrylamide. To ensure that there was no spill-over between lanes, in some gels one or more lanes were left empty as shown here for the middle lane labeled E in the right FP1 blot. To fully resolve α11.2 short and long forms, the 100 kDa marker was run close to the bottom except in the right panel. In this experiment, electrophoresis of the same extracts used for α11.2 immunoblotting was terminated before the dye front reached the bottom. Probing for b-actin showed that comparable amounts of protein were present in each extract from the different WT and KI mice. (B) Cav1.2 was immunoprecipitated from brain extracts from conditional KO and WT mice with the FP1 antibody before SDS-PAGE in gels polymerized from 6% acrylamide and immunoblotting with the indicated antibodies. To fully separate α11.2 short and long forms, electrophoresis was performed until the 100 kDa marker was near the bottoms of the gels. For all antibodies, the ~210 and 250 kDa bands were nearly or completely absent in cKO samples. Raw data for Figure 3. Analysis of α11.2 size forms by SDS-PAGE with increasing acrylamide concentrations. Original source images for Figure 3: Cav1.2 was immunoprecipitated from mouse brain extracts (Triton X-100) with the FP1 antibody against α11.2 before fractionation by SDS-PAGE in gels polymerized from 5, 7, 9, 11, and 13% acrylamide followed by immunoblotting with the indicated antibodies. Two different prestained marker protein sets were used to estimate MR. Raw data for Figure 4. Mouse and rat α11.2 short forms co-migrate with α11.2 truncated at residue 1800 in the middle of the c-terminus. Original source images for Figure 4: HEK293T cells were transfected with full length or truncated (D1800) a11.2 plus a2d1 and b2a. HEK293T cells and rat and mouse brain slices were extracted with 1% Triton X-100 before immunoprecipitation of a11.2, SDS-PAGE in gels polymerized from 8% acrylamide, and immunoblotting with the indicated antibodies. (A) The full length form of a11.2 expressed in HEK293 cells migrated with an apparent MR of 250 kDa and is detected by FP1, pS1700 and pS1928. Truncated D1800 a11.2 migrated with an apparent MR of 210 kDa and is detected by FP1 and pS1700 but not pS1928. (B) The a11.2 short and long form appear only partially resolved because the weak a11.2 signals in HEK293 cell samples required long exposure times. The upper band as detected by CNC1 after FP1 immunoprecipitation from rat and mouse forebrain slices and cortical slices co-migrated with the full length form of a11.2 expressed in HEK293 cells, while the lower band co-migrated with the truncated D1800 a11.2 expressed in HEK293 cells. Sometimes, as seen here, a significant portion of the pore-forming subunit aggregated at the interface between stacking and resolving gels. This unresolved fraction (thick arrow) is not representative of its true molecular mass and not shown in the main figures. Raw data for Figure 5. Surface biotinylation labels α11.2 size forms with apparent MR > 200 kDa in rat cortical and forebrain slices. Original source images for Figure 5: Cortical and forebrain slices were surface biotinylated and solubilized before pulldown with NeutrAvidin Sepharose, SDS-PAGE in 8% acrylamide gels, and immunoblotting with CNC1 and FP1. Control reflects slices mock treated without Sulfo-NHS-SS-biotin to demonstrate specificity of pulldown. Twenty mL lysate was also directly loaded for comparison. Raw data for Figure 6. Differential recognition of the strong 150 kDa FP1 band in lysate and weak 150 kDa band by FP1, CNC1, and ACC-003 after IP of α11.2 with FP1. Original source images for Figure 6: Immunoblots with CNC1 (A,B), FP1 (C), and ACC-003 (D,E) of Triton X-100 extracts from WT mice (lysate) and after immunoprecipitation with FP1 from cKO and WT mice. Gels were polymerized from 8% acrylamide. Note that a weak 150 kDa band is detected by CNC1, FP1, and ACC-003 after enrichment of α11.2 by immunoprecipitation with FP1 but the strongly immunoreactive 150 kDa band detected by FP1 in lysate is not detectable by either CNC1 or ACC-003.