Scinderin, a novel Ca2+‐activated actin filament‐severing protein, has been purified to homogeneity from bovine adrenal medulla using a combination of several chromatographic procedures. The protein has an apparent mol. wt of 79,600 +/‐ 450 daltons, three isoforms (pIs 6.0, 6.1 and 6.2) and two Ca2+ binding sites (Kd 5.85 x 10(‐7) M, Bmax 0.81 mol Ca2+/mol protein and Kd 2.85 x 10(‐6) M, Bmax 1.87 mol Ca2+/mol protein). Scinderin interacts with F‐actin in the presence of Ca2+ and produces a decrease in the viscosity of actin gels as a result of F‐actin filament severing as demonstrated by electron microscopy. Scinderin is a structurally different protein from chromaffin cell gelsolin, another actin filament‐severing protein described. Scinderin and gelsolin have different mol. wts, isoelectric points, amino acid composition and yield different peptide maps after limited proteolytic digestion by either Staphylococcus V8 protease or chymotrypsin. Moreover, scinderin antibodies do not cross‐react with gelsolin and gelsolin antibodies fail to recognize scinderin. Immunofluorescence with anti‐scinderin demonstrated that this protein is mainly localized in the subplasmalemma region of the chromaffin cell. Immunoblotting tests with the same antibodies indicated that scinderin is also expressed in brain and anterior as well as posterior pituitary. Presence of scinderin and gelsolin, two Ca2+‐dependent actin filament‐severing proteins in the same tissue, suggests the possibility of synergistic functions by the two proteins in the control of cellular actin filament networks. Alternatively, the actin filament‐severing activity of the two proteins might be under the control of different transduction and modulating influences.

Scinderin is a calcium-dependent actin filament-severing protein recently discovered in the chromaffin cells of adrenal medulla. In view of the wide tissue distribution of gelsolin, another actin filament-severing protein, experiments were performed to determine the tissue expression of scinderin. Extracts prepared from different bovine tissues were tested by actin-DNase I Sepharose 4B-binding procedure and immunoprecipitation followed by immunoblotting with scinderin and gelsolin antibodies. Among the tissues tested, scinderin was found to be present in the adrenal medulla, brain, anterior and posterior pituitaries, kidney, salivary gland and testis. Scinderin was not found in liver, plasma, skeletal and heart muscles. Gelsolin was expressed in all of the above tissues. The results suggest that scinderin seems to be restricted to tissues with high secretory activity.

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