HCaRG increases renal cell migration by a TGF-α autocrine loop mechanism

Abstract

We have shown previously that the hypertension-related, calcium-regulated gene (HCaRG) is involved in the control of renal cell proliferation and differentiation (Devlin AM, Solban N, Tremblay S, Gutkowska J, Schurch W, Orlov SN, Lewanczuk R, Hamet P, and Tremblay J. Am J Physiol Renal Physiol 284: F753–F762, 2003). To determine whether HCaRG plays a role in kidney repair after injury, we extended our studies on the cellular function of HCaRG by comparing cell migration of two kidney cell lines [HEK293 and Madin-Darby canine kidney (MDCK)-C7] stably transfected with the plasmid alone or with a plasmid containing HCaRG cDNA. HCaRG-expressing HEK293 cells, which undergo lower proliferation, migrated faster than control cells and presented greater adhesiveness to the extracellular matrix. Faster migration was also observed for the MDCK-C7 cells, after they were stably transfected with HCaRG cDNA. HCaRG overexpression induced major morphological changes in HEK293 cells, including the formation of lamellipodia. Expression microarrays of HCaRG-expressing HEK293 cells revealed the elevated expression of several genes known to be involved in cell migration and lamellipodia formation, including transforming growth factor-α (TGF-α), galectins, autotaxins and fibronectin. These cells exhibited augmented synthesis and release of activated TGF-α. Conditioned medium from HCaRG-expressing cells stimulated the migration and induced significant morphological changes in control cells, in part, through activation of the TFG-α/EGF receptor. Together, these data support a role for HCaRG in kidney repair after injury through its effect on renal cell migration and TGF-α secretion.