Analyzing the functions of Translationally controlled tumor protein2 during growth, development and autophagy of Dictyostelium discoideum

Translationally controlled tumor protein (TCTP) is a well conserved and ubiquitously expressed multifunctional protein found in many organisms and is involved in many pathophysiological processes like cell proliferation, differentiation, development and cell death. The role of TCTP in anti-apoptosis and cancer metastasis makes it a promising candidate for cancer therapy. Dictyostelium discoideum, a protist, has two isoforms (TCTP1 and TCTP2, now referred to as TPT1 and TPT2) of which we have earlier elucidated TPT1. Here, we analyzed the role of TPT2 in this organism. tpt2 transcript was present throughout growth and development and is localized in the prestalk/stalk regions of multicellular structures developed. tpt2 gene was disrupted with a BSR cassette using a double homologous recombination method. Disruption of tpt2 gene (tpt2‾) exhibit reduced cell proliferation and nutrient-uptake. Additionally, development in tpt2‾ was delayed by 2 h, formed small-sized aggregates that developed into stalky fruiting bodies with reduced spore viability. In contrast, overexpressed tpt2 (tpt2^OE) showed increased cell proliferation and development, formed large-size aggregates that developed into spory fruiting bodies with increased spore viability. TPT2 regulates prestalk/prespore ratio and cell-type differentiation as abrogation of tpt2 gene resulted in altered localization of cell-type markers and an inclination towards the prestalk/stalk pathway while tpt2^OE showed a prespore/spore biasness when mixed with wild-type cells. Deletion of either tpt1 or tpt2 gene showed increased autophagic flux indicating their involvement in negative regulation of autophagy. This study provides insights into the intricate involvement of TCTP in cellular dynamics and development of D. discoideum.