Triple A patient cells suffering from mitotic defects fail to localize PGRMC1 to mitotic kinetochore fibers

Abstract

HIGHLIGHT SUMMARYO_LIInvestigating cell division in human adrenal cells we show that proliferation is decreased upon overexpression of ALADIN, PGRMC1 or PGRMC2.\nC_LIO_LIIn immunofluorescence experiments using human adrenal cells and triple A patient fibroblasts we observed that during cell division PGRMC1 localizes to the microtubule kinetochore-fibers in metaphase and to the mid-body in telophase.\nC_LIO_LIDepletion of ALADIN results in mis-localization of Aurora A and PGRMC1 in metaphase cells of the human adrenal cell line and fibroblasts derived from patients with triple A syndrome.\nC_LIO_LIIn real time PCR using RNA of fibroblasts of triple A syndrome patients and healthy controls we measured an increased expression of PGRMC2 in cells with ALADIN mis-function compared to the control cells.\nC_LIO_LIWe hypothesize that a loss of the regulatory interaction between ALADIN and PGRMC2 leads to an over-regulation and over-expression of PGRMC2 and displaces PGRMC1 at the metaphase spindle. This diminishing of PGRMC1 concentration at kinetochore fibers may lead to mitotic errors and pro - liferation arrest.\nC_LI\n\nABSTRACTMembrane-associated progesterone receptors are restricted to the endoplasmic reticulum and are shown to regulate the activity of cytochrome P450 enzymes which are involved in steroidogenesis or drug detoxification. PGRMC1 and PGRMC2 belong to this group of microsomal receptors and are of interest due to their suspected role during cell cycle. PGRMC1 and PGRMC2 are thought to bind to each other thereby suppressing entry into mitosis. We could previously report that PGRMC2 interacts with the nucleoporin ALADIN which when mutated results in the autosomal recessive disorder triple A syndrome. ALADIN is a novel regulator of mitotic controller Aurora kinase A and depletion of this nucleoporin leads to microtubule instability. In the current study, we present that proliferation is decreased when ALADIN, PGRMC1 or PGRMC2 are over-expressed. Furthermore, we find that depletion of ALADIN results in mis-localization of Aurora kinase A and PGRMC1 in metaphase cells. Additionally, PGRMC2 is over-expressed in triple A patient fibroblasts. Our results emphasize the possibility that loss of the regulatory interaction between ALADIN and PGRMC2 gives rise to a depletion of PGRMC1 at kinetochore fibers and to mitotic errors. This observation may explain part of the symptoms seen in triple A syndrome patients.