Micrograph of a HeLa cell expressing green fluorescent protein (GFP) tagged myosin-10 together with calmodulin-like protein. Note the abundant fluorescent myosin-10 puncta in filopodial extensions. Image taken by Richard D. Bennett (Mayo Graduate School PhD student, Molecular Biology track)

Topological model of the plasma membrane calcium pump. The pump is shown in the autoinhibited state, in which the calmodulin-binding domain (CaM-BD) binds to intramolecular sites on the first and second hydrophilic loops. The ten membrane-spanning domains, the catalytic phosphorylation site (~P) and the ATP-binding site (AS) are indicated. The PDZ domain-binding region present in some calcium pump splice variants is marked by a circled PDZ. Arrows point to the regions (“hotspots” A and C) where isoform diversity is created by alternative RNA splicing. For details, see Strehler, E.E. and Treiman, M., Curr. Mol. Med. 4:323-335 (2004).

Alternative splicing affects the membrane localization of the plasma membrane calcium pump (PMCA) isoform 2b. Full-length PMCA2w/b, PMCA2x/b, and PMCA2z/b (constructs schematically shown on top) were expressed in polarized MDCK (dog kidney epithelial) cells, and the localization of the pumps was studied by confocal fluorescence microscopy. PMCA2 was detected with an isoform-specific antibody followed by an Alexa-488 labeled secondary antibody (green). Nuclei were stained with DAPI. PMCA2w/b shows apical localization in addition to basal and lateral staining (left panel), whereas PMCA2x/b and PMCA2z/b are confined to the basal and lateral membranes (middle and right panel). Corresponding x:z sections are shown below the en face views. Arrows indicate the height at which the en face sections were captured. Bar, 20 µm. For details, see Chicka, M.C. and Strehler, E.E., J. Biol. Chem. 278:18464-18470 (2003).