ATP competes with PIP2 for binding to gelsolin

Abstract

Gelsolin is a severing and capping protein that targets filamentous actin and regulates filament lengths near plasma membranes, contributing to cell movement and plasma membrane morphology. Gelsolin binds to the plasma membrane via phosphatidylinositol 4,5-bisphosphate (PIP2) in a state that cannot cap F-actin, and gelsolin-capped actin filaments are uncapped by PIP2 leading to filament elongation. The process by which gelsolin is removed from PIP2 at the plasma membrane is currently unknown. Gelsolin also binds ATP with unknown function. Here we characterize the role of ATP on PIP2-gelsolin complex dynamics. Fluorophore-labeled PIP2 and ATP were used to study their interactions with gelsolin using steady-state fluorescence anisotropy, and Alexa488-labeled gelsolin was utilized to reconstitute the regulation of gelsolin binding to PIP2-containing phospholipid vesicles by ATP. Under physiological salt conditions ATP competes with PIP2 for binding to gelsolin, while calcium causes the release of ATP from gelsolin. These data suggest a cycle for gelsolin activity. Firstly, calcium activates ATP-bound gelsolin allowing it to sever and cap F-actin. Secondly, PIP2-binding removes the gelsolin cap from F-actin at low calcium levels, leading to filament elongation. Finally, ATP competes with PIP2 to release the calcium-free ATP-bound gelsolin, allowing it to undergo a further round of severing.

Steroidal glycoalkaloids fromSolanum nigrumtarget cytoskeletal proteins: anin silicoanalysis

“…Cofilin also displayed binding to magnesium ( K d 109.84 mM), in accordance to previous reports (Hamill et al, 2016). As is evident from Table 3, most of the studied proteins displayed potent binding to ATP (Kambe et al, 1992; Szatmári et al, 2018). However, the dissociation constant(s) of a majority of phytoconstituents from S. nigrum were found to be lower than those for ATP with respect to the studied target protein(s).…”

A Ciliary View of the Immunological Synapse

“…A further level of complexity is added by the fact that phosphoinositide signals are important for the coordination of cytoskeleton rearrangements. In ciliated cells PtdIns(4,5)P 2 activates multiple regulatory proteins of the actin cytoskeleton (e.g., WASP family members, cofilin and gelsolin) promoting actin polymerization [196,197,198,199]. In T cells PtdIns(4,5)P 2 is able to promote the polymerization of cortical actin at the IS as well by interacting with a number of actin-related proteins, including Exrin/Radaxin/Moesin and WASP [200,201].…”

Peer Review #1 of "Steroidal glycoalkaloids from Solanum nigrum target cytoskeletal proteins: an in silico analysis (v0.1)"

“…Cofilin also displayed binding to magnesium (K d 109.84 mM), in accordance to 385 previous reports(Hamill et al, 2016). As is evident fromTable 3, most of the studied proteins displayed 386 potent binding to ATP(Kambe et al, 1992;Szatmári et al, 2018). However, the dissociation constant(s)…”