Cell-cell and virus-cell fusion assay-based analyses of alanine insertion mutants in the distal α9 portion of the JRFL gp41 subunit from HIV-1.
J Biol Chem
; 294(14): 5677-5687, 2019 04 05.
Article
in En
| MEDLINE
| ID: mdl-30737278
ABSTRACT
Membrane fusion is the first essential step in HIV-1 replication. The gp41 subunit of HIV-1 envelope protein (Env), a class I fusion protein, achieves membrane fusion by forming a structure called a six-helix bundle composed of N- and C-terminal heptad repeats. We have recently shown that the distal portion of the α9 helix in the C-terminal heptad repeat of X4-tropic HXB2 Env plays a critical role in the late-stage membrane fusion and viral infection. Here, we used R5-tropic JRFL Env and constructed six alanine insertion mutants, 641+A to 646+A, in the further distal portion of α9 where several glutamine residues are conserved (the number corresponds to the position of the inserted alanine in JRFL Env). 644+A showed the most severe defect in syncytia formation. Decreased fusion pore formation activity, revealed by a dual split protein assay, was observed in all mutants except 641+A. Sequence analysis and substitution of inserted 644A with Gln revealed that the glutamine residue at position 644 that forms complex hydrogen-bond networks with other polar residues on the surface of the six-helix bundle is critical for cell-cell fusion. We also developed a split NanoLuc® (Nluc) reporter-based assay specific to the virus-cell membrane fusion step to analyze several of the mutants. Interestingly syncytia-competent mutants failed to display Nluc activities. In addition to defective fusion activity, a reduction of Env incorporation into virions may further contribute to differences in cell-cell and virus-cell fusions.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Biological Assay
/
HIV Envelope Protein gp41
/
Mutagenesis, Insertional
/
HIV-1
/
Virus Internalization
/
Membrane Fusion
Limits:
Humans
Language:
En
Journal:
J Biol Chem
Year:
2019
Type:
Article