Calcium signaling modulates the dynamics of cilia and flagella

Decoding the Bell-Shaped Calcium Spikes in Phosphorylation Cycles of Flagella

“…These elementary Ca 2+ signals are the building-blocks by which recruitment of the complex Ca 2+ signals is constructed. This includes the localized “Ca 2+ clouds” drifting along MTDs within the scope of our model [ 2 , 16 , 21 ].…”

“…We earlier established [ 21 , 34 ] and further refined [ 2 , 16 ] the polyelectrolyte concept of MTs aimed to explain how Ca 2+ ions, albeit present in nM to μM concentrations in the cytosol, use MTs as a buffers to condense close around their filaments and C-termini (CTTs). Moreover, the accumulated Ca 2+ ions form bell-shaped “Ca 2+ clouds” that propagate along MTs much faster than it could be achieved by simple three-dimensional diffusion.…”

“…Equation (1) can be solved if the local Ca 2+ concentration within a single spike is taken to be our bell-shaped “Ca 2+ cloud”, [ 2 , 16 ]: where is the direction of an MT doublet, is the tubulin dimer length, is the drift velocity of “Ca 2+ cloud”, t stands for the time variable, and is the amplitude of Ca 2+ concentration within each spike. We should fix the position of a specific dynein motor with accompanying regulatory proteins (CaM, CaMKII, IC138) involved in the motor’s activations.…”

“…The figure shows the main ingredients; nine microtubule doublets, the central microtubule pair, radial spokes, nexin linkers, and two sets of different dynein motors (outer dynein arms and inner dynein arms). Some accessory proteins are also added [ 2 ].…”

Electrical Propagation of Condensed and Diffuse Ions Along Actin Filaments

“…In addition, Tunneling nanotubes (TNTs) are a cell-to-cell connection composed of actin filaments surrounded by a lipid membrane that can transport calcium over distances up to 100 micrometers (Sartori-Rupp et al, 2019;Marzo, Gousset, and Zurzolo, 2012;Gerdes, Rustom, and Wang, 2013). Nevertheless, whether actin is a pathway for calcium to the stereocilia of the inner ear, or involved in cellular calcium signaling by storage and release, actin proteins and calcium ions have recently demonstrated to have more roles than previously understood (Tuszynski et al, 2018b;Sataric et al, 2020;Lange and Brandt, 1996). One new promising mode of ion transport inside neurons is through the cytoskeleton where actin filaments and microtubules may be a direct path for transporting divalent ions like calcium or magnesium (Sataric, Sekulic, and Sataric, 2015;Tuszynski et al, 2018a;Sataric et al, 2009;Craddock, Tuszynski, and Hameroff, 2012;Priel et al, 2008).…”