Abstract 5118: Cysteine (C)-X-C receptor 4 undergoes transportin 1 dependent nuclear localization and is functional at the nucleus of metastatic prostate cancer cells.
Authors: Don-Salu-Hewage Ayesha S. , Chan Siu Y. , McAndrews Kathleen , Chetram Mahandranauth A. , Dawson Michelle R. , Hinton Cimona V. 
Published: August 2014

The G-Protein coupled receptor (GPCR) Cysteine (C)-X-C Receptor 4 (CXCR4) plays an important role in prostate cancer (PCa) metastasis. To date, considerable evidence support the presence of GPCRs at the plasma membrane (PM), or within the perinuclear/nuclear compartments of cells and have been suggested to regulate a number of physiological processes including cell proliferation, survival, inflammatory responses and tumorigenesis. In accordance with previous clinical observations in diverse tumor tissues, we observed ubiquitous expression of CXCR4 in metastatic PCa tissues and several PCa cells lines. Additionally, Gαi immunoprecipitation and calcium mobilization studies elucidated that nuclear CXCR4 was functional and participated in G-protein signaling. However, a mechanism by which CXCR4 is translocated to the nucleus is poorly understood.An initial search of the CXCR4 sequence via the PSORT II NLS prediction software program revealed a putative, nontraditional nuclear localization sequence (NLS), “RPRK” in CXCR4.Additionally,the members of karyopherin beta (β) family, Karyopherin-β2 or Transportin 1 (TRN1) were reported to be involved in transportation of various cargos into the nucleus, including the chemokine GPCRs. Collectively, based on our results and previous studies, we suggest that the NLS, “RPRK”and TRN1 play a role in translocation of CXCR4 into the nucleus of advanced PCa. To determine the involvement of “RPRK," manipulations of the NLS revealed that single point mutations of basic resides within the NLS was insufficient to eliminate to abrogate nuclear translocation of CXCR4. However, when the NLS was deleted, nuclear CXCR4 was not detected. Additionally, TRN1 immunoprecipitation and siRNA-TRN1 studies delineated an association between CXCR4 and TRN1,and that nuclear translocation of CXCR4 depended on TRN1. Little information is available about nuclear GPCRs and nuclear CXCR4 in cancer. Thus, the significance of the study is that since CXCR4 is a major signaling receptor involved in PCa metastasis, the dualistic localization pattern and function at the nucleus may encourage recurrence,metastasis and poorer prognosis after tumors have been treated with therapy that targets CXCR4.In conclusion, our studies will provide insight to the development of therapeutics towards CXCR4 and transport mechanisms, as current therapy targets membrane receptors, which may be ineffective if CXCR4 is translocated and functional inside of the cell.

Citation Format: Ayesha S. Don-Salu-Hewage, Siu Y. Chan, Kathleen McAndrews, Mahandranauth A. Chetram, Michelle R. Dawson, Cimona V. Hinton. Cysteine (C)-X-C receptor 4 undergoes transportin 1 dependent nuclear localization and is functional at the nucleus of metastatic prostate cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5118. doi:10.1158/1538-7445.AM2013-5118