Nuclear Localization of Phospholipase D1 Mediates the Activation of Nuclear Protein Kinase Cα and Extracellular Signal-regulated Kinase Signaling Pathways

Young Hoon Jang,Do Sik Min

doi:10.1074/jbc.m110.162602

Abstract

Recent studies highlight the existence of a nuclear lipid metabolism related to cellular proliferation. However, the importance of nuclear phosphatidylcholine (PC) metabolism is poorly understood. Therefore, we were interested in nuclear PC as a source of second messengers and, particularly, nuclear localization of PC-specific phospholipase D (PLD). In the present study we have identified the nuclear localization sequence (NLS) of PLD1 whose mutation abolished its nuclear import. Recently, we reported that caspase-mediated cleavage of PLD1 generates the N-terminal fragment (NF-PLD1) and C-terminal fragment (CF-PLD1). Here we show that CF-PLD1 but not NF-PLD1, is exclusively imported into the nucleus via its functional NLS, whereas only some portions of intact PLD1 were localized into the nucleus. The NLS of intact PLD1 or CF-PLD1 is required for interaction with importin-β, which is known to mediate nuclear import. The amount of intact PLD1 or CF-PLD1 translocated into nucleus is correlated with its binding affinity with importin-β. Ultimately, nuclear localization of intact PLD1 but not CF-PLD1 mediates the activation of nuclear protein kinase Cα and extracellular signal-regulated kinase signaling pathways. Taken together, we propose that nuclear localization of PLD1 via the NLS and its interaction with importin-β may provide new insights on the functional role of nuclear PLD1 signaling.

Highlights

Involved in the control of cell proliferation and gene expression [4, 5]
Endogenous PLD1 Is Detected in the Nucleus—Evidence is being accumulated on the importance of internal nuclear lipid metabolism
To our knowledge this study is the first demonstration that nuclear localization of PLD1 mediates the activation of nuclear PKC␣ and extracellular signal-regulated kinase (ERK) signaling pathways

Summary

Introduction

Involved in the control of cell proliferation and gene expression [4, 5]. Nuclear phosphoinositides have received a considerable degree of attention. To address this latter possibility, HEK293 cells expressing endogenous PLD1 were treated with an inhibitor of the CRM-1 exportin pathway, LMB, and the localization of PLD1 was examined (Fig. 2A). An intact GFP-PLD1 was detected in both cytosolic and nuclear fraction, whereas GFPNLM-PLD1 was localized exclusively in the cytosol but not in the nucleus.

Results

Conclusion