Abstract
Members of the highly conserved class of BEACH domain containing proteins (BDCPs) have been established as broad facilitators of protein–protein interactions and membrane dynamics in the context of human diseases like albinism, bleeding diathesis, impaired cellular immunity, cancer predisposition, and neurological dysfunctions. Also, the Arabidopsis thaliana BDCP SPIRRIG (SPI) is important for membrane integrity, as spi mutants exhibit split vacuoles. In this work, we report a novel molecular function of the BDCP SPI in ribonucleoprotein particle formation. We show that SPI interacts with the P-body core component DECAPPING PROTEIN 1 (DCP1), associates to mRNA processing bodies (P-bodies), and regulates their assembly upon salt stress. The finding that spi mutants exhibit salt hypersensitivity suggests that the local function of SPI at P-bodies is of biological relevance. Transcriptome-wide analysis revealed qualitative differences in the salt stress-regulated transcriptional response of Col-0 and spi. We show that SPI regulates the salt stress-dependent post-transcriptional stabilization, cytoplasmic agglomeration, and localization to P-bodies of a subset of salt stress-regulated mRNAs. Finally, we show that the PH-BEACH domains of SPI and its human homolog FAN (Factor Associated with Neutral sphingomyelinase activation) interact with DCP1 isoforms from plants, mammals, and yeast, suggesting the evolutionary conservation of an association of BDCPs and P-bodies.
Highlights
beige and Chediak Higashi (BEACH) domain containing proteins (BDCPs) represent a highly conserved protein family in eukaryotes [1,2]
BEACH domain containing proteins (BDCP) are known to be important for membrane dynamics such as vesicle transport, membrane fission and fusion events, and autophagy
Gluthatione S-Transferase (GST)/His6-fusions of SPI-PBW were efficiently bound to resins labeled with Maltose Binding Protein (MBP)-tagged DECAPPING PROTEIN1 (DCP1), while no binding was detected with the negative control MBP alone (Fig 1C)
Summary
BEACH (beige and Chediak Higashi) domain containing proteins (BDCPs) represent a highly conserved protein family in eukaryotes [1,2]. The BEACH domain was described as a protein motif in the human lysosomal trafficking regulator protein (LYST). Mutations in LYST cause the autosomal recessive human Chediak Higashi Syndrome (CHS) [3]. Individuals concerned suffer from severe morphological symptoms, like decreased pigmentation, bleeding diathesis, impaired cellular immunity [6], cancer growth [7], and neurological dysfunctions [8]. All experimental data point to a role of BDCPs in the regulation of membrane dynamics. Mutations in BDCPs have been shown to impair diverse cellular mechanisms, including vesicle transport, membrane fission and fusion events, receptor signaling, autophagy, and apoptosis [9]
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