Synaptopodin regulates the actin-bundling activity of α-actinin in an isoform-specific manner
J. Clin. Invest. Katsuhiko Asanuma, et al. 115:1188 doi:10.1172/JCI23371 [Go to this article.]

Figure 4
Synaptopodin colocalizes with α-actinin in tissues and cultured cells. (A) In the adult kidney, synaptopodin colocalizes with α-actinin-4 in podocytes (magnification, ×650). (B) Synaptopodin colocalizes with α-actinin-4 along actin filaments in differentiated cultured wild-type podocytes (magnification, ×650). (C) During kidney development, α-actinin-4 is already found in undifferentiated podocytes (arrows) of the S-shaped body stage (S) that have a cortical actin cytoskeleton. In contrast, synaptopodin is first found in the capillary loop stage (C) when podocytes start to develop long, unbranched contractile actin bundles (magnification, ×450). (D) Codistribution of synaptopodin with α-actinin-2 in the CA1, CA3, and dendate gyrus (DG) regions in the hippocampus of a 6-month-old wild-type mouse (magnification, ×650). (E) Lack of synaptopodin and downregulation of α-actinin-2 labeling in all regions of the hippocampus in an age-matched synpo^–/– mouse (magnification, ×650). (F) Western blot analysis of cytosolic extract from glomeruli (left) and brains (right) of 6-month-old wild-type and synpo^–/– mice. The levels of α-actinin-4 are not different between wild-type and synpo^–/– mice. In contrast, there is a strong downregulation of α-actinin-2 in the brains of synpo^–/– mice. Equal protein loading was confirmed by reprobing for tubulin.