Several adaptor proteins promote intracellular localisation of the transporter MRP4/ABCC4 in platelets and haematopoietic cells

Abstract

The multidrug resistance protein 4 (MRP4/ABCC4) has been identified as an important transporter for signalling molecules including cyclic nucleotides and several lipid mediators in platelets and may thus represent a novel target to interfere with platelet function. Besides its localisation in the plasma membrane, MRP4 has been also detected in the membrane of dense granules in resting platelets. In polarised cells it is localised at the basolateral or apical plasma membrane. To date, the mechanism of MRP4 trafficking has not been elucidated; protein interactions may regulate both the localisation and function of this transporter. We approached this issue by searching for interacting proteins by in vitro binding assays, followed by immunoblotting and mass spectrometry, and by visualising their co-localisation in platelets and haematopoietic cells. We identified the PDZ domain containing scaffold proteins ezrin-binding protein 50 (EBP50/NHERF1), postsynaptic density protein 95 (PSD95), and sorting nexin 27 (SNX27), but also the adaptor protein complex 3 subunit β3A (AP3B1) and the heat shock protein HSP90 as putative interaction partners of MRP4. The knock-down of SNX27, PSD95, and AP3B1 by siRNA in megakaryoblastic leukaemia cells led to a redistribution of MRP4 from intracellular structures to the plasma membrane. Inhibition of HSP90 led to a diminished expression and retention of MRP4 in the endoplasmic reticulum. These results indicate that MRP4 localisation and function are regulated by multiple protein interactions. Changes in the adaptor proteins can hence lead to altered localisation and function of the transporter.

HPV16 E6 promotes cervical cancer cell migration and invasion by downregulation of NHERF1

“…Whereas, NHERF1 accelerated cell migration and invasion in triple‐negative breast cancer cells and glioblastoma cells . NHERF1, as a signaling adaptor, can regulate multiple cellular processes via interaction with its different binding partners . NHERF1 is reported to suppress breast cancer cell when it scaffolds with tumor suppressors, whereas it becomes oncogenic when it interacts with oncoproteins .…”

“…47 NHERF1, as a signaling adaptor, can regulate multiple cellular processes via interaction with its different binding partners. 48 NHERF1 is reported to suppress breast cancer cell when it scaffolds with tumor suppressors, 49 whereas it becomes oncogenic when it interacts with oncoproteins. 50,51 Whether NHERF1 acts as a tumor suppressor or oncoprotein might lie partly on the tissue-specific distribution of its target proteins.…”

The Novel Regulatory Role of lncRNA-miRNA-mRNA Axis in Amyotrophic Lateral Sclerosis: An Integrated Bioinformatics Analysis

“…AD and ALS are both neurodegenerative diseases, and PICALM has been proven to be the causative gene of AD [52][53][54]. In addition, there are a large number of published studies confirming that AP3B1 is related to type 2 Hermansky-Pudlak syndrome [55][56][57][58][59][60][61][62][63][64]. Although these four genes (SYNRG, ITSN2, PICALM, and AP3B1) have not been reported in the literature on ALS, the SYNRG, ITSN2, PICALM, AP3B1, and AAK1 genes are regulated by MALAT1, and the proteins encoded by these genes are all related to clathrin.…”

Role of adaptin protein complexes in intracellular trafficking and their impact on diseases

“…Additionally, AP3B1 variants found in humans were detected in patients with bleeding diathesis, presumably caused by platelet disorder [180]. AP3B1 also interacts with multidrug resistance protein 4 (MRP4) [181] and is involved in vesicle-associated membrane protein 8 (VAMP8) trafficking and Weibel-Palade body maturation [182] which are crucial processes in platelet function. AP3B1 mutation was reported to cause neutropenia, a deficiency in white blood cells, in humans, as well as in canine cyclic hematopoiesis in dogs; however, this mutation only resulted in decreased hematopoietic progenitor and decreased granulocyte mobilization upon signaling in pearl mice [183].…”