Deletion of Dictyostelium tpc2 gene forms multi-tipped structures, regulates autophagy and cell-type patterning

Area of Science:

• Cell Biology
• Developmental Biology
• Ion Channel Physiology

Background:

• Two pore channels (TPCs) are voltage-gated ion channels crucial for releasing Ca2+ from acidic intracellular stores.
• TPCs are vital in both animal and plant kingdoms, regulating essential cellular processes.
• Starvation triggers multicellular development in Dictyostelium discoideum, a process influenced by intracellular calcium levels.

Purpose of the Study:

• To investigate the role of TPC2 in the development, differentiation, and autophagy of Dictyostelium discoideum.
• To understand how TPC2 influences cell-type determination and patterning during multicellular development.

Main Methods:

• Localization studies of TPC2 protein within lysosome-like acidic vesicles.
• Analysis of Dictyostelium development and differentiation in wild-type, tpc2 knockout (tpc2-), and TPC2 overexpressing (tpc2OE) strains.
• Measurement of intracellular cAMP levels, pinocytosis rates, and autophagic flux.

Main Results:

• TPC2 protein localizes to lysosome-like acidic vesicles, influencing stalk cell bias.
• Deletion of tpc2 resulted in defective, delayed development and altered cell-type patterning, while TPC2 overexpression accelerated development.
• TPC2 regulates cell-substrate adhesion, cellular morphology, intracellular cAMP levels, and pinocytosis, with tpc2 deletion reducing autophagic flux.

Conclusions:

• TPC2 is indispensable for efficient development and differentiation in Dictyostelium.
• TPC2 plays a critical role in supporting autophagic cell death and establishing correct cell-type patterning.
• Reduced intracellular calcium due to TPC2 deletion inhibits autophagic flux, highlighting calcium's role in autophagy.