Dataset for: TRPM7-mediated spontaneous Ca<sup>2+</sup> entry regulates the proliferation and differentiation of human leukaemia cell line K562

AIM: Continuous Ca<sup>2+</sup> influx is essential to maintain intracellular Ca<sup>2+</sup> homeostasis and its dysregulation leads to a variety of cellular dysfunctions. In this study, we explored the functional roles of spontaneous Ca<sup>2+</sup> influx for the proliferation and differentiation of a human erythromyeloid leukaemia cell line K562. METHODS: mRNA/protein expressions were assessed by the real-time RT-PCR, Western blotting and immunocytochemical staining. Intracellular Ca<sup>2+</sup> concentration ([Ca<sup>2+</sup>]<sub>i</sub>) and ionic currents were measured by fluorescent imaging and patch clamping techniques, respectively. Cell counting/viability and colorimetric assays were applied to assess proliferation rate and haemoglobin synthesis, respectively. RESULTS: Elimination of extracellular Ca<sup>2+</sup> decreased basal [Ca<sup>2+</sup>]<sub>i</sub> in proliferating K562 cells. Cation channel blockers such as SK&F96365, 2-APB, Gd<sup>3+</sup> and FTY720 dose-dependently decreased basal [Ca<sup>2+</sup>]<sub>i</sub>. A spontaneously active inward current (I<sub>spont</sub>) contributive to basal [Ca<sup>2+</sup>]<sub>i</sub> was identified by the nystatin-perforated whole-cell recording. I<sub>spont</sub> permeated Ca<sup>2+</sup> comparably to Na<sup>+</sup>, and was greatly eliminated by siRNA targeting TRPM7, a melastatin member of the transient receptor potential (TRP) superfamily. Consistent with these findings, TRPM7 immune-reactivity was detected by Western blotting, and immunofluorescence representing TRPM7 was found localized to the K562 cell membrane. Strikingly, all these procedures, i.e. Ca<sup>2+</sup> removal, TRPM7 blockers and siRNA-mediated TRPM7 knockdown significantly retarded the growth and suppressed hemin-induced γ-globin and haemoglobin syntheses in K562 cells, respectively, both of which appeared associated with the inhibition of ERK activation. CONCLUSIONS: These results collectively suggest that spontaneous Ca<sup>2+</sup> influx through constitutively active TRPM7 channels may critically regulate both proliferative and erythroid differentiation potentials of K562 cells.