Guanine nucleotide-induced Ca2+ release in permeabilized murine thymocytes

Area of Science:

• Cellular biology
• Molecular signaling
• Immunology

Background:

• Calcium ions (Ca2+) are critical intracellular messengers involved in numerous cellular processes.
• Internal Ca2+ stores play a vital role in regulating cytoplasmic Ca2+ concentrations.
• Inositol trisphosphate (IP3) is a well-known mediator of Ca2+ release from internal stores.

Purpose of the Study:

• To investigate the role of guanosine triphosphate (GTP) in inducing Ca2+ release from internal stores.
• To compare the mechanism of GTP-induced Ca2+ release with that of IP3-induced Ca2+ release.
• To identify nucleotides that can induce Ca2+ release in permeabilized murine thymocytes.

Main Methods:

• Permeabilization of murine thymocytes.
• Loading of thymocytes with Ca2+ using ATP.
• Induction of Ca2+ release using various nucleotides, including GTP and IP3.
• Dose-response analysis of GTP-induced Ca2+ release.
• Assessment of the effect of nucleotide analogs and other nucleotides on Ca2+ release.

Main Results:

• GTP induced Ca2+ release from internal stores in a dose-dependent manner, with half-maximal release at 0.5 microM and maximal release at 10 microM.
• The GTP effect was inhibited by non-hydrolyzable GTP analogs (GTP gamma S, GMPPNP) and UTP.
• Inositol trisphosphate (ITP) also induced Ca2+ release, but other tested nucleotides did not.
• Sequential addition of GTP and IP3 resulted in further Ca2+ release, indicating distinct pathways.

Conclusions:

• GTP is capable of inducing Ca2+ release from internal stores in murine thymocytes.
• The mechanism of GTP-mediated Ca2+ release appears to be distinct from that of IP3-mediated Ca2+ release.
• These findings contribute to understanding the complex regulation of intracellular calcium signaling.