T CCR5 Receptor ConstructsMutant CCR5 receptor constructs were generated by PCR using Deep Vent high fidelity DNA polymerase (New England Biolabs, Ipswich, MA) and the wild type human CCR5 chemokine receptor cDNA, cloned into the pcDNA3.1(+) expression vector (Invitrogen, Carlsbad, CA), as template. The Ballesteros and Weinstein amino acid numbering system [34] is used to facilitate comparison of CCR5 with other rhodopsin-like GPCRs. The generic residue number consists of the TMS, 1 to 7, in which the residue is located, followed by the position relative to the most 11967625 conserved residue of the TMS, which is CAL-120 custom synthesis designated number 50. The generic number is followed by the number of the residue in the sequence of the CCR5 receptor. For example, the Asp125 residue in the conserved DRY motif of the CCR5 receptor is designated Asp3.49(125), because it immediately precedes the most conserved residue in TMS3, Arg3.50(126). Asp3.49(125) was mutated to Ala (Asp3.49(125)Ala) and Asn (Asp3.49(125)Asn), whereas the Thr2.56(82) residue in TMS2 of CCR5 was mutated to Pro (Thr2.56(82)Pro), Lys (Thr2.56(82)Lys) and Arg (Thr2.56(82)Arg) and Arg6.32(225), in the third intracellular loop, was mutated to Gln, Ala, Asp and Glu. The Arg6.32(225)Gln construct was used as the template for the double mutants, Thr2.56(82)Lys/Arg6.32(225)Gln and Thr2.56(82)Pro/Arg6.32(225)Gln. Mutant constructs were sequenced and subcloned into the pcDNA3.1(+) and pcDNA3.1/ Hygro(+) expression vectors.Cell Culture and TransfectionHEK 293 cells (ATCC) were maintained in Dulbecco’s Modified Eagle’s Medium (DMEM, Gibco, Invitrogen, Paisley, Scotland) containing fetal bovine serum (FBS, 10 , Highveld Biologicals, Johannesburg, South Africa) and cultured at 37uC with 10 CO2. HEK-Gqi cells were maintained in DMEM supplemented with FBS (10 ) and G418 (200 mg/ml). HOSCD4.pBABE-puro and HOS-CD4-CCR5 cells were maintained in DMEM supplemented with FBS (10 ) and puromycin (1 mg/ ml), whereas the same cell lines stably transfected with pHIV1LTR-Luc to generate the cell lines, HOS-CD4-Luc and HOSCD4-CCR5-Luc, were maintained with FBS, puromycin (1 mg/ ml) and G418 (400 mg/ml). Cells were plated into 10 cm2 dishes (3?6106 cells, Corning, Cambridge, USA) in a final volume of 10 ml DMEM with FBS (10 ) 24 h before transfection. DNA constructs (6 mg) were incubated with FuGene HD (30 ml, Roche order 57773-63-4 Diagnostics Corp., Indianapolis, USA) in serum-free DMEM (room temperature, 30 min) and added directly to the 10 ml medium in the 10 cm dishes. Cells were incubated overnight (37uC; 5 CO2). For stable transfections, selection antibiotics were added two days later and individual colonies of antibiotic-resistant cells were harvested and propagated. Attempts to stably transfect CCR5 constructs into HOS-CD4-Luc cells were unsuccessful. HOS-CD4-Luc cells transiently transfected with wild type and mutant CCR5 constructs were cultured in the presence of hygromycin B (200 mg/ml) for two days to increase the proportion of receptorexpressing cells and thus compensate for low transfection efficiency.Materials and Methods DNA Constructs, Cell Lines and ProteinsThe chimeric G protein construct, Gaqi, which allows receptors that usually activate the Gi/o family of G proteins to stimulate inositol phosphate (IP) signaling [30] was prepared by site-directed mutagenesis, cloned into the pcDNA3.1(+) expression vector (Invitrogen, Carlsbad, CA) and stably expressed in HEK 293 cells (HEK-Gqi) as previously described [22]. The HIV-1C.T CCR5 Receptor ConstructsMutant CCR5 receptor constructs were generated by PCR using Deep Vent high fidelity DNA polymerase (New England Biolabs, Ipswich, MA) and the wild type human CCR5 chemokine receptor cDNA, cloned into the pcDNA3.1(+) expression vector (Invitrogen, Carlsbad, CA), as template. The Ballesteros and Weinstein amino acid numbering system [34] is used to facilitate comparison of CCR5 with other rhodopsin-like GPCRs. The generic residue number consists of the TMS, 1 to 7, in which the residue is located, followed by the position relative to the most 11967625 conserved residue of the TMS, which is designated number 50. The generic number is followed by the number of the residue in the sequence of the CCR5 receptor. For example, the Asp125 residue in the conserved DRY motif of the CCR5 receptor is designated Asp3.49(125), because it immediately precedes the most conserved residue in TMS3, Arg3.50(126). Asp3.49(125) was mutated to Ala (Asp3.49(125)Ala) and Asn (Asp3.49(125)Asn), whereas the Thr2.56(82) residue in TMS2 of CCR5 was mutated to Pro (Thr2.56(82)Pro), Lys (Thr2.56(82)Lys) and Arg (Thr2.56(82)Arg) and Arg6.32(225), in the third intracellular loop, was mutated to Gln, Ala, Asp and Glu. The Arg6.32(225)Gln construct was used as the template for the double mutants, Thr2.56(82)Lys/Arg6.32(225)Gln and Thr2.56(82)Pro/Arg6.32(225)Gln. Mutant constructs were sequenced and subcloned into the pcDNA3.1(+) and pcDNA3.1/ Hygro(+) expression vectors.Cell Culture and TransfectionHEK 293 cells (ATCC) were maintained in Dulbecco’s Modified Eagle’s Medium (DMEM, Gibco, Invitrogen, Paisley, Scotland) containing fetal bovine serum (FBS, 10 , Highveld Biologicals, Johannesburg, South Africa) and cultured at 37uC with 10 CO2. HEK-Gqi cells were maintained in DMEM supplemented with FBS (10 ) and G418 (200 mg/ml). HOSCD4.pBABE-puro and HOS-CD4-CCR5 cells were maintained in DMEM supplemented with FBS (10 ) and puromycin (1 mg/ ml), whereas the same cell lines stably transfected with pHIV1LTR-Luc to generate the cell lines, HOS-CD4-Luc and HOSCD4-CCR5-Luc, were maintained with FBS, puromycin (1 mg/ ml) and G418 (400 mg/ml). Cells were plated into 10 cm2 dishes (3?6106 cells, Corning, Cambridge, USA) in a final volume of 10 ml DMEM with FBS (10 ) 24 h before transfection. DNA constructs (6 mg) were incubated with FuGene HD (30 ml, Roche Diagnostics Corp., Indianapolis, USA) in serum-free DMEM (room temperature, 30 min) and added directly to the 10 ml medium in the 10 cm dishes. Cells were incubated overnight (37uC; 5 CO2). For stable transfections, selection antibiotics were added two days later and individual colonies of antibiotic-resistant cells were harvested and propagated. Attempts to stably transfect CCR5 constructs into HOS-CD4-Luc cells were unsuccessful. HOS-CD4-Luc cells transiently transfected with wild type and mutant CCR5 constructs were cultured in the presence of hygromycin B (200 mg/ml) for two days to increase the proportion of receptorexpressing cells and thus compensate for low transfection efficiency.Materials and Methods DNA Constructs, Cell Lines and ProteinsThe chimeric G protein construct, Gaqi, which allows receptors that usually activate the Gi/o family of G proteins to stimulate inositol phosphate (IP) signaling [30] was prepared by site-directed mutagenesis, cloned into the pcDNA3.1(+) expression vector (Invitrogen, Carlsbad, CA) and stably expressed in HEK 293 cells (HEK-Gqi) as previously described [22]. The HIV-1C.
