Oxidation of fatty acids uses l-carnitine to transport acyl moieties to mitochondria in a so-called carnitine shuttle. The process of β-oxidation also takes place in cancer cells. The majority of carnitine comes from the diet and is transported to the cell by ubiquitously expressed organic cation transporter novel family member 2 (OCTN2)/solute carrier family 22 member 5 (SLC22A5). The expression of SLC22A5 is regulated by transcription factors peroxisome proliferator-activated receptors (PPARs) and estrogen receptor. Transporter delivery to the cell surface, as well as transport activity are controlled by OCTN2 interaction with other proteins, such as PDZ-domain containing proteins, protein phosphatase PP2A, caveolin-1, protein kinase C. SLC22A5 expression is altered in many types of cancer, giving an advantage to some of them by supplying carnitine for β-oxidation, thus providing an alternative to glucose source of energy for growth and proliferation. On the other hand, SLC22A5 can also transport several chemotherapeutics used in clinics, leading to cancer cell death.

A plasma membrane amino acid transporter B^0,+ (ATB^0,+), encoded by the SLC6A14 gene, is specific for neutral and basic amino acids. It is up-regulated in several types of malignant cancers. Neurotransmitter transporters of the SLC6 family interact with specific SEC24 proteins of the COPII complex along their pathway from the endoplasmic reticulum (ER) to Golgi. This study focused on the possible role of SEC24 proteins in ATB^0,+ trafficking. Rat ATB^0,+ was expressed in HEK293 cells, its localization and trafficking were examined by Western blot, deglycosylation, immunofluorescence (co-localization with ER and trans-Golgi markers) and biotinylation. The expression of ATB^0,+ at the plasma membrane was decreased by dominant negative mutants of SAR1, a GTPase, whose activity triggers the formation of the COPII complex. ATB^0,+ co-precipitated with SEC24C (but not with the remaining isoforms A, B and D). This interaction was confirmed by immunocytochemistry and the proximity ligation assay. Co-localization of SEC24C with endogenous ATB^0,+ was also observed in MCF-7 breast cancer cells. Contrary to the endogenous transporter, part of the overexpressed ATB^0,+ is directed to proteolysis, a process significantly reversed by a proteasome inhibitor bortezomib. Co-transfection with a SEC24C dominant negative mutant attenuated ATB^0,+ expression at the plasma membrane, due to proteolytic degradation. These results support a hypothesis that lysine at position +2 downstream of the ER export "RI" motif on the cargo protein is crucial for SEC24C binding and for further trafficking to the Golgi. Moreover, there is an equilibrium between ER export and degradation mechanisms in case of overexpressed transporter.

SpringerPlus 2015, 4(Suppl 1):L1 MicroRNAs (miRNAs) are short, 22-25 nucleotide long transcripts that may suppress entire signaling pathways by interacting with the 3'-untranslated region (3'-UTR) of coding mRNA targets, interrupting translation and inducing degradation of these targets. The long 3'-UTRs of brain transcripts compared to other tissues predict important roles for brain miRNAs. Supporting this notion, we found that brain miRNAs co-evolved with their target transcripts, that non-coding pseudogenes with miRNA recognition elements compete with brain coding mRNAs on their miRNA interactions, and that Single Nucleotide Polymorphisms (SNPs) on such pseudogenes are enriched in mental diseases including autism and schizophrenia, but not Alzheimer's disease (AD). Focusing on evolutionarily conserved and primate-specifi c miRNA controllers of cholinergic signaling ('CholinomiRs'), we fi nd modifi ed CholinomiR levels in the brain and/or nucleated blood cells of patients with AD and Parkinson's disease, with treatment-related diff erences in their levels and prominent impact on the cognitive and anti-infl ammatory consequences of cholinergic signals. Examples include the acetylcholinesterase (AChE)-targeted evolutionarily conserved miR-132, whose levels decline drastically in the AD brain. Furthermore, we found that interruption of AChE mRNA's interaction with the primatespecifi c CholinomiR-608 in carriers of a SNP in the AChE's miR-608 binding site induces domino-like eff ects that reduce the levels of many other miR-608 targets. Young, healthy carriers of this SNP express 40% higher brain AChE activity than others, potentially aff ecting the responsiveness to AD's anti-AChE therapeutics, and show elevated trait anxiety, infl ammation and hypertension. Non-coding regions aff ecting miRNA-target interactions in neurodegenerative brains thus merit special attention.