Liquid chromatography/mass spectrometry analysis revealing preferential occurrence of non-arachidonate-containing phosphatidylinositol bisphosphate species in nuclei and changes in their levels during cell cycle.

Phosphatidylinositol phosphates (PtdInsPs) are present within the nucleus, as well as in the membrane. In this mass spectrometry study, different acyl-containing species of endonuclear PtdInsPs were analyzed in order to clearly understand the role of individual molecular species. A (34:1) acyl-containing phosphatidylinositol bisphosphate [PtdInsP(2)(34:1)] and PtdInsP(2)(36:1) were preferentially detected in envelope-less nuclei prepared from various cultured human cells, while PtdInsP(2)(38:4) was not a major component within these nuclei. A significant amount of PtdInsP(2)(34:0) was detected in the HeLa cell nucleus, but not in the A431 and THP-1 cell nuclei. During the cell cycle in HeLa cells, PtdInsP(2)(34:0) levels increased in the early G1 phase, and then gradually decreased through S phase, while PtdInsP(2)(34:1) levels tended to decrease only in late G1 phase and PtdInsP(2)(38:4) did not change significantly. Thus, individual PtdInsP(2) species apparently play different roles in nuclear events based on individual regulation of endonuclear levels. The non-arachidonate-containing species were also detected in normal human blood and fluids, suggesting that these minor species may have unique functions in the human body. The techniques used in this study will be applied to clinical studies on a PtdInsPs metabolism.