Gelsolin expression increases β 1 ‐integrin affinity and L1210 cell adhesion

Integrins are functionally regulated by “inside‐out” signaling, in that stimulus‐induced signaling pathways act on the intracellular integrin tail to regulate the activity of the receptor on the outside. Both a change in conformation (affinity) and clustering (avidity/valency) of the receptors occurs, but the mechanisms that regulate inside out signaling are not completely understood. Previously, we identified gelsolin in a proteomics screen to identify proteins involved in inside‐out control of integrins using the lymphocytic leukemia cell line L1210. Furthermore, we showed that gelsolin was involved in affinity regulation of β 1 ‐integrins in the leukemic cell line U937. Here, we examined how gelsolin regulates β 1 ‐integrin affinity in the leukemia cell line L1210. We show that gelsolin is mainly expressed at the cell membrane and is present near β 1 ‐integrins. The role for actin polymerization in integrin affinity regulation was examined using the actin modulating agent jasplakinolide, which decreased β 1 ‐integrin affinity. Similarly, knock‐down of gelsolin in L1210 cells also decreased β 1 ‐integrin affinity and cell adhesion to collagen. These data suggest that increased actin polymerization through gelsolin regulates β 1 ‐integrin affinity and cell adhesion. © 2013 Wiley Periodicals, Inc.