The plates were incubated upside-down at 30 C for 57 days to obtain well separated colonies having a diameter of 13 mm. have FPXXM and FPXM sequences, respectively. With its common distribution in the nervous system and its predominantly hydrophobic interactions, GEC1 may have chaperone-like effects for many cell surface proteins along the biosynthesis pathway. opioid receptor (KOPR)2is one of the three major types of opioid receptors mediating effects of opioid drugs and endogenous opioid peptides. Activation of KOPR generates many effectsin vivo, for example antinociception (especially for visceral chemical pain, antipruritis, and water diuresis (1). The KOPR agonist nalfurafine (TRK-820) is used clinically in Sweden for the treatment of uremic pruritus in kidney dialysis patients (2). Because KOPR agonists produce profound sedative effects, it has been proposed that KOPR agonists may be useful in treating mania, antagonists as anti-depressants, and partial agonists for the management of mania depressive disorder (3). KOPR antagonists may also be useful for curbing cocaine craving PROTAC MDM2 Degrader-3 and as anti-anxiety drugs (4,5). KOPR, a member of the rhodopsin subfamily of the seven-transmembrane receptor superfamily, is usually coupled preferentially to pertussis toxin-sensitive G proteins, namely Gi/oproteins (6). KOPR has been found to interact with several non-G protein-binding partners, such as Na+,H+-exchanger regulatory factor-1/ezrin-radixin-moesin-binding phosphoprotein-50 and the opioid receptor. These interactions have influence on transmission transduction and trafficking of the receptor (79). By yeast two-hybrid (Y2H) assay Rabbit polyclonal to CD10 using the hKOPR C-tail to screen a human brain cDNA library, we recognized GEC1, also named GABAAreceptor-associated protein like 1 (GABARAPL1), to be a binding partner of hKOPR PROTAC MDM2 Degrader-3 (10). GEC1 cDNA was first cloned as an early estrogen-regulated mRNA from guinea pig endometrial glandular epithelial cells by Pellerinet al. (11). Subsequently, it was cloned from other species, including human and house mouse (12). Interestingly, the amino acid sequences of GEC1 are completely conserved among all these species except orangutan, in which Arg99substitutes for His99. Northern blot and immunoblotting analyses revealed that it has common tissue distribution (1214). PROTAC MDM2 Degrader-3 In particular, GEC1 was found to be abundant in the central nervous system and expressed throughout the rat brain (14,15). This wide tissue distribution and the high sequence identity across species strongly suggest that GEC1 has important biological functions in mammalian cells. Based on sequence similarity, GEC1 is usually classified as a member of microtubule-associated proteins (MAPs), which also include GABAAreceptor-associated protein (GABARAP), Golgi-associated ATPase enhancer of 16 kDa (GATE16), GABARAP-like 3 (GABARAPL3), light chain 3 (LC3) of MAP 1A/1B, and the yeast autophagy protein 8 (Atg8) (12,13). Among these homologues, GEC1 share the highest identity with GABARAPL3 (93%), followed by GABARAP (86%), GATE16 (61%), Atg8 (55%), and LC3 (30%). A growing body of evidence shows that this protein family is closely related to two unique biological functions. Studies mainly on GABARAP, GATE16, and GEC1 show that they promote intracellular protein trafficking by enhancing vesicle fusion (10,1621). In addition, they facilitate degradation of proteins and intracellular organelles via autophagy-related pathways, which is usually bolstered largely by research on Atg8 and LC3 (22,23). We previously reported that GEC1 interacted with the hKOPR C-tail and enhanced cell surface levels of hKOPR stably expressed in CHO cells. GEC1 expression enhances hKOPR expression through facilitating its anterograde trafficking along the protein biosynthesis pathway without affecting degradation of the receptor (10). This represented the first biological function reported for GEC1. Mansuyet al.(24) demonstrated that GEC1 interacted with tubulin and promoted microtubule bundlingin vitro, and that green fluorescence protein-tagged GEC1 was localized in the perinuclear vesicles with a scattered pattern. Our electron microscopic studies in the rat brain showed that GEC1 was associated with ER, Golgi apparatus, endosome-like vesicles, and plasma membranes and scattered in cytoplasm in neurons (14). In addition,N-ethylmaleimide-sensitive factor, a protein critical for intracellular membrane-trafficking events, binds directly to GEC1 (10). In this study, we employed Y2H techniques to determine the amino acid residues in both GEC1 and hKOPR C-tail involved in the conversation. Further studies were then carried out in mammalian cells to examine if elimination of the conversation affected the effect of GEC1 on hKOPR expression. In addition, we generated a molecular model of GEC1 based on the x-ray crystal structure of GABARAP and found that the residues involved in hKOPR binding created hydrophobic patches on the exterior surface of GEC1. Moreover, we found that the cytosolic tail of AMPA receptor subunit GluR1 has the same FPXXM motif as that found in the hKOPR C-tail to be involved in GEC1 binding and that GEC1 expression up-regulated GluR1. == EXPERIMENTAL PROCEDURES == == Materials == [15,16-3H]Diprenorphine (56 Ci/mmol) was purchased from PerkinElmer Life Sciences. Naloxone and rabbit anti-FLAG polyclonal antibody were purchased from Sigma. Cell media (Dulbecco’s altered Eagle’s medium/F-12, 1:1), Opti-MEM I reduced serum, fetal bovine serum.
