gms | German Medical Science

A rise in cytosolic free Ca²⁺ concentration, ([Ca²⁺]_i), could be an important stimulus for cell growth of SV40 immortalized human corneal epithelial cells (HCEP-SV40). This effect is generally a result of depletion of intracellular Ca²⁺ stores which induces capacitative Ca²⁺ entry (CCE). The aim of this study was to investigate induction of CCE in HCEP-SV40 through stored-operated channels (SOC) which are associated with transient receptor potential (TRP) channel activity.

Effects of the SOC blocker Ni²⁺ on CCE amplitude were determined on [Ca²⁺]_i in fura2-loaded HCEP-SV40 cells with a single cell fluorescence video imaging system (J. Biol. Chem. 1985; 260: 3440-3450). SOC currents were measured by patch-clamp technique (Pflügers Arch. 1981; 391:85-100).

Cyclopiazonic acid (CPA) at 10 μM followed by 5 mM extracellular Ca²⁺ induced CCE that had a large amplitude. It stabilized at 560 ± 50 nM; (n = 5). Ni²⁺ (0.5 mM), an inhibitor of SOC, reversibly decreased CCE amplitude to 380 ± 84 nM. Following washout, recovery occurred to 469 ± 73 nM (n = 5 different coverslips). In addition, patch-clamp recordings revealed SOC currents which were increased after application of 10 μM CPA.

HCEP express Ni²⁺-sensitive SOC channels whose components include transient receptor potential proteins (TRPs). This implicates an expanded role for this family of ion channels in the physiology of the human corneal epithelium. Additional studies characterizing TRP channel subtypes and their putative association with receptors (i.e. tyrosine receptor kinases) are necessary for a better understanding of HCEP cell function and dysfunction in different corneal diseases.

Supported in part: DFG (PL 150/10‑1; PR EY04795)