Schematic diagram depicting the proposed role of Ca21-RhoA signaling pathway in polyamine-dependent
cell migration after wounding. The process of cell migration is initiated by polyamine-induced expression of the
Kv1.1 channel gene in intestinal epithelial cells. Polyamines stimulate the Kv1.1 gene expression probably by
directly binding to the gene promoter and/or indirectly enhancing the function of transcriptional factors such as
c-Fos. The resultant increase in Kv channel activity causes membrane hyperpolarization, increases the driving
force for Ca21 influx, and raises [Ca21]cyt. By increasing the rate of RhoA protein synthesis and stability, the
elevation of [Ca21]cyt induces RhoA expression. Activated RhoA stimulates myosin light chain (MLC) phosphorylation
by enhancing the activity of MLC kinase (MLCK), increases the formation of actomyosin stress fibers, and
thus induces cell migration. In addition, RhoA activity is also regulated through the cross talk with Rac proteins,
and the balance of Rho and Rac activities appears to be a critical factor controlling cellular migratory phenotype
during restitution after wounding.