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Calcium- and proton-dependent relocation of annexin A6 in Jurkat T cells stimulated for interleukin-2 secretion

100%

Podszywalow-Bartnicka P., Strzelecka-Kiliszek A., Bandorowicz-Pikula J., Pikula S.

Annexin A6 (AnxA6) is a Ca2+-dependent membrane-binding protein involved in vesicular traffic. The likely participation of AnxA6 in the response of lymphocytes to Ca2+ signals has not been investigated yet. The present study focuses on intracellular relocation of AnxA6 in human Jurkat T lymphoblasts upon stimulation followed by transient increase of intracellular [Ca2+] and exocytosis of interleukin-2 (IL-2). Stimulation of the cells under different experimental conditions (by lowering pH and/or by rising extracellular [Ca2+] in the presence of ionomycin) induced time-dependent transients of intracellular [Ca2+] and concomitant changes in AnxA6 intracellular localization and in IL-2 secretion, with only minor effects on cell viability and apoptosis. In resting conditions (in the presence of EGTA or with no ionophore) AnxA6 was localized uniformly in the cytosol, whereas it translocated to vesicular structures beneath the plasma membrane within 5 min following stimulation of Jurkat T cells and rise of intracellular [Ca2+] at pH 7.4. Lowering the extracellular pH value from 7.4 to 6.0 significantly enhanced this process. AnxA6 changed its location from the cytosol to the secretory granules and early endosomes which seem to represent membranous targets for annexin. In conclusion, AnxA6 is sensitive to variations in intracellular [Ca2+] upon stimulation of Jurkat T cells, as manifested by a switch in its intracellular localization from the cytosol to vesicular structures located in close proximity to the plasma membrane, suggestive of participation of AnxA6 in calcium- and proton-dependent secretion of cytokines by lymphocytes.

Transport functions and physiological significance of 76 kDa Ral-binding GTPase activating protein (RLIP76).

64%

Awasthi S., Sharma R., Yang Y., Singhal S. S., Pikula S., Bandorowicz-Pikula J., Singh S. V., Zimniak P., Awasthi Y. C.

vol. 49

issue 4

855-867

We have recently demonstrated that a previously known Ral-binding GTPase activating protein, RLIP76, can also catalyze ATP-dependent transport of various structurally unrelated xeno- and endobiotics irrespective of their net charge (Awasthi et al., 2000, Biochemistry, 39: 9327). RLIP76 is a non-ATP binding cassette (ABC) protein but it has two ATP-binding sites and shows basal ATPase activity which is stimulated in the presence of its transport substrates (allocrites) such as doxorubicin (DOX) and S-(2,4-dinitrophenyl) glutathione (DNP-SG). Proteoliposomes reconstituted with purified RLIP76 catalyze ATP-dependent, saturable transport of DOX, as well as of glutathione-conjugates including leukotrienes (LTC4) and the GSH-conjugate of 4-hydroxynonenal (GS-HNE). In erythrocytes the majority of transport activity for DOX, GS-HNE, and LTC4 is accounted for by RLIP76. Cells exposed to mild oxidative stress show a rapid and transient induction of RLIP76 resulting in an increased efflux of GS-HNE and acquire resistance to oxidative stress mediated toxicity and apoptosis. Cells transfected with RLIP76 acquire resistance to DOX through increased efflux of the drug suggesting its possible role in the mechanisms of drug-resistance. In this article, we discuss the significance of transport functions of RLIP76 highlighting its role in the defense mechanisms against oxidative injury, and modulation of signaling mechanisms.

The roles of annexins and alkaline phosphatase in mineralization process.

64%

Balcerzak M., Hamade E., Zhang L., Pikula S., Azzar G., Radisson J., Bandorowicz-Pikula J., Buchet R.

Acta Biochimica Polonica

2003

vol. 50

issue 4

1019-1038

In this review the roles of specific proteins during the first step of mineralization and nucleation are discussed. Mineralization is initiated inside the extracellular organelles-matrix vesicles (MVs). MVs, containing relatively high concentrations of Ca2+ and inorganic phosphate (Pgi), create an optimal environment to induce the formation of hydroxyapatite (HA). Special attention is given to two families of proteins present in MVs, annexins (AnxAs) and tissue-nonspecific alkaline phosphatases (TNAPs). Both families participate in the formation of HA crystals. AnxAs are Ca2+- and lipid-binding proteins, which are involved in Ca2+ homeostasis in bone cells and in extracellular MVs. AnxAs form calcium ion channels within the membrane of MVs. Although the mechanisms of ion channel formation by AnxAs are not well understood, evidence is provided that acidic pH or GTP contribute to this process. Furthermore, low molecular mass ligands, as vitamin A derivatives, can modulate the activity of MVs by interacting with AnxAs and affecting their expression. AnxAs and other anionic proteins are also involved in the crystal nucleation. The second family of proteins, TNAPs, is associated with Pi homeostasis, and can hydrolyse a variety of phosphate compounds. ATP is released in the extracellular matrix, where it can be hydrolyzed by TNAPs, ATP hydrolases and nucleoside triphosphate (NTP) pyrophosphohydrolases. However, TNAP is probably not responsible for ATP-dependent Ca2+/phosphate complex formation. It can hydrolyse pyrophosphate (PPi), a known inhibitor of HA formation and a byproduct of NTP pyrophosphohydrolases. In this respect, antagonistic activities of TNAPs and NTP pyrophosphohydrolases can regulate the mineralization process.

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3 Acta Biochimica Polonica

1 2007

1 2003

1 2002

3 Bandorowicz-Pikula J.

3 Pikula S.

1 Awasthi S.

1 Awasthi Y. C.

1 Azzar G.

1 Balcerzak M.

1 Buchet R.

1 Hamade E.

1 Podszywalow-Bartnicka P.

1 Radisson J.

1 Sharma R.

1 Singh S. V.

1 Singhal S. S.

1 Strzelecka-Kiliszek A.

1 Yang Y.

1 Zhang L.

1 Zimniak P.

Search results

Calcium- and proton-dependent relocation of annexin A6 in Jurkat T cells stimulated for interleukin-2 secretion

Transport functions and physiological significance of 76 kDa Ral-binding GTPase activating protein (RLIP76).

The roles of annexins and alkaline phosphatase in mineralization process.