title: TRPC6 regulates cell cycle progression by modulating membrane potential in bone marrow stromal cells.
abstract: OBJECTIVE
  Ca(2+) influx is important for cell cycle progression, but the mechanisms involved seem to vary. We investigated the potential roles of transient receptor potential (TRP) channels and store-operated Ca(2+) entry (SOCE)-related molecules STIM (stromal interaction molecule)/Orai in the cell cycle progression of rat bone marrow stromal cells (BMSCs), a reliable therapeutic resource for regenerative medicine.
  
  
  METHODS
  PCR and immunoblot analyses were used to examine mRNA and protein levels, fluorescence imaging and patch clamping for Ca(2+) influx and membrane potential measurements, and flow cytometry for cell cycle analysis.
  
  
  RESULTS
  Cell cycle synchronization of BMSCs revealed S phase-specific enhancement of TRPC1, STIM and Orai mRNA and protein expression. In contrast, TRPC6 expression decreased in the S phase and increased in the G1 phase. Resting membrane potential (RMP) of BMSCs was most negative and positive in the S and G1 phases, respectively, and was accompanied by an enhancement and attenuation of SOCE respectively. Chemically depolarizing/hyperpolarizing the membrane erased these differences in SOCE magnitude during the cell cycle. siRNA knockdown of TRPC6 produced a negative shift in RMP, increased SOCE and caused redistribution of BMSCs with increased populations in the S and G2 /M phases and accumulation of cyclins A2 and B1. A low concentration of Gd(3+) (1 μM) suppressed BMSC proliferation at its concentration to inhibit SOC channels relatively specifically.
  
  
  CONCLUSIONS
  TRPC6, by changing the membrane potential, plays a pivotal role in controlling the SOCE magnitude, which is critical for cell cycle progression of BMSCs. This finding provides a new therapeutic strategy for regulating BMSC proliferation.
authors.affiliation: Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Ichikawa
authors.forename: Ryuji
authors.initials: R
authors.lastname: Inoue
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011916:Rats, Inbred F344; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C560435:STIM2 protein, rat; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D050052:TRPC Cation Channels; C492145:Trpc6 protein, rat; C096351:transient receptor potential cation channel, subfamily C, member 1