Inhibition of telomerase activity and induction of apoptosis by Rhodospirillum rubrum L‐asparaginase in cancer Jurkat cell line and normal human CD4+ T lymphocytes

Abstract

Rhodospirillum rubrum L‐asparaginase mutant E149R, V150P, F151T (RrA) down‐regulates telomerase activity due to its ability to inhibit the expression of telomerase catalytic subunit hTERT. The aim of this study was to define the effect of short‐term and long‐term RrA exposure on proliferation of cancer Jurkat cell line and normal human CD4+ T lymphocytes. RrA could inhibit telomerase activity in dose‐ and time‐dependent manner in both Jurkat and normal CD4+ T cells. Continuous RrA exposure of these cells resulted in shortening of telomeres followed by cell cycle inhibition, replicative senescence, and development of apoptosis. Complete death of Jurkat cells was observed at the day 25 of RrA exposure while normal CD4+ T cells died at the day 50 due to the initial longer length of telomeres. Removal of RrA from senescent cells led to a reactivation of hTERT expression, restoration telomerase activity, re‐elongation of telomeres after 48 h of cultivation, and survival of cells. These findings demonstrate that proliferation of cancer and normal telomerase‐positive cells can be limited by continuous telomerase inhibition with RrA. Longer telomeres of normal CD4+ T lymphocytes make such cells more sustainable to RrA exposure that could give them an advantage during anti‐telomerase therapy. These results should facilitate further investigations of RrA as a potent anti‐telomerase therapeutic protein.

Penetration into Cancer Cells via Clathrin-Dependent Mechanism Allows L-Asparaginase from Rhodospirillum rubrum to Inhibit Telomerase

“…It was previously shown that RrA can inhibit telomerase in cancer cells and normal human lymphocytes by inhibiting the expression of its catalytic subunit hTERT (human telomerase reverse transcriptase) [ 10 , 11 ]. We checked whether other L-ASNases have similar effects on telomerase by incubating Jurkat cells with enzymes of different origins.…”

“…An unexpected antitelomerase activity came from the observation that the rather well-studied L-ASNase from Rhodospirillum rubrum (RrA) can suppress proliferation and induces replicative senescence in acute leukemia Jurkat cancer cell line at non-toxic concentrations [ 11 ]. All known mechanisms of antiproliferative activity of L-ASNases rely on their ability to hydrolyze L-asparagine in the cell microenvironment or in a close proximity to cellular membranes.…”

“…A very surprising cytotoxic asparagine-independent mechanism was described for a Rhodospirillum rubrum mutant L-ASNase with E149R, V150P, and F151T amino acid substitutions (RrA). RrA demonstrated regulatory capacity and could suppress telomerase activity in a number of human cancer cell lines, normal activated CD4 + T lymphocytes and xenografts of human solid tumors [ 10 , 11 ]. The role of RrA in telomerase suppression indirectly indicates its intracellular or even intranuclear localization as well as its ability to penetrate into the cellular membrane.…”

LB Crystallization and Preliminary X-ray Diffraction Analysis of L-Asparaginase from Rhodospirillum rubrum

“…activity in vivo [14][15][16][17][18]. RrA subunit has small molecular weight (18 kDa; monomer contains 172 amino acids).…”

“…KVS NIMA LB through), spreading 100 µm of protein solution with Hamilton syringe and compressing protein monolayer to a surface pressure of 20 mN/m by means of a Langmuir-Blodgett teflon barriers [16][17][18]…”