Rabbit anti-tissue transglutaminase polyclonal antibody (clone ab421) was from Novus Biologicals (Littleton, CO); anti-active caspase 3 antibody (no. 557035) from BD Biosciences (San Diego, CA); mouse monoclonal anti-β actin antibody (clone AC-15) from Sigma-Aldrich (St. Louis, MO); goat anti-rabbit AlexaFluor 594 antibodies and goat anti-mouse AlexaFluor 488 antibodies from Invitrogen-Molecular Probes (Eugene, OR); recombinant human TNF-α or TNFSF1A (no. 210-TA-010), MTT reagent (TA5355, TACS) and detergent reagent from R&D Systems, Inc. (Minneapolis, MN); a cell viability assay (ApopTag Fluorescein Kit; S7110) from Chemicon (Temecula, CA); mono-dansyl cadaverine (MDC) and fluorescent cadaverine (no. A10466) from Invitrogen-Molecular Probes; cresyl violet (no. 192) from Harleco (Gibbstown, NY); guinea pig liver transglutaminase (no. T5398) from Sigma-Aldrich; a protein delivery system (Chariot) from ActiveMotif (Carlsbad, CA); glass coverslips (no. 70462, Secureslip) from Electron Microscopy Sciences (Hatfield, PA); predesigned siRNA (Silencer) from Ambion (Austin, TX); RNA transfection reagent (no. 301705, HiPerfect) from Qiagen (Valencia, CA); first-strand beads (Ready-To-Go You-Prime) from GE Healthcare (Piscataway, NJ); and PCR master mix (AmpErase UNG) MGB probes (Taqman) for TGM-2 (assay Hs 00190278_m1) from Applied Biosystems (ABI; Foster City, CA).