Role of the matrix protein in the virion association of the human immunodeficiency virus type 1 envelope glycoprotein

“However, virions with N-terminal CA mutations often display marked infectivity defects and aberrant core morphology by EM (Jowett et al., 1992; von Poblotzki et al., 1993; Wang and Barklis, 1993; Dorfman et al., 1994a; Reicin et al., 1995, 1996).”

“…Wang & Barklis, 1993; Wang et al., 1993; Wills et al., 1991; Yuan et al., 1993; Zhou et al., 1994) and interacts with the cytoplasmic tail of TM (Dorfman et al., 1994b; Freed & Martin, 1996; Freed et al., 1994; Freed & Martin, 1995; Mammano et al., 1995; Wang & Barklis, 1993; Wang et al., 1993;…”

“Mutations in the CA of murine leukemia virus (17, 35, 57), Mason-Pfizer monkey virus (59), and HIV-1 (5, 11, 40, 62) also disrupt virion formation.”

“(v) HIV-1 MA facilitated the incorporation of HIV-1 Env into visna virus–HIV-1 chimeric particles (7).”

“Fourth, several reports describe the introduction of point mutations and deletions in the MA coding region of the HIV1, SIV, and MPMV genomes (52, 71, 139, 218, 303).”

“The Gag polyprotein specifically incorporates several viral elements into nascent virions, including viral genomic RNA (33), the env glycoprotein (14, 70), and the pol-encoded enzymes (44, 56).”

“A variety of functions have been proposed for the HIV-1 MA, including roles in virus assembly (2, 14, 36, 47), virus entry (44), nuclear localization (3), and incorporation of envelope glycoproteins into virus particles (6, 45).”

“After the 14-day preculture differentiation period, cells were transferred to 96-well Nunc tissue culture plates (1-67008) at 10(5) cells per well.”

“It is possible that reductions in the levels of virion-associated gpl20, which have been observed for other MA mutations (11, 76), affect the infectivity of some of our MA mutants.”

“This latter observation could be the result of several factors: (i) reduced immunoreactivity previously described for amino acid 20 substitutions (33) and for other MA mutants (6, 10), (ii) Pr55 instability, and (iii) increased rate of Pr55 processing, also observed previously for residue 20 mutants (33, 34).”

“Deletions (9, 48, 52) and single amino acid substitutions (13, 15, 33) in MA can block HIV-1 envelope glycoprotein incorporation into virus particles, and HIV-1 MA has been implicated in early events postinfection (for a review, see reference 11).”

“In-frame deletions in the MA coding region were generated by recombination of previously described MA mutants (Dorfman et al., 1994).”

“Under these conditions, HIV-1 surface glycoprotein shed into the medium is excluded from the virion pellet (8).”

“Other functions have been described for CT, including interaction with the viral matrix protein (48, 62, 72, 160, 260), targeting to vesicles (56, 129, 194), as well as interaction with other proteins (15, 102, 152, 171, 252).”

“Recent studies have shown that the HIV-1 MA domain is both essential and sufficient for incorporation of the viral envelope glycoprotein into nascent particles (13, 46).”

“In the case of human immunodeficiency virus type 1 (HIV-1), Env is likely to be incorporated into virions by association of its cytoplasmic tail with the matrix protein (MA) of Gag (12, 14, 15, 20, 61, 62).”

“Evidence for a direct Gag-Env interaction includes the findings that (i) mutations in the HIV-1 MA can block HIV-1 Env incorporation (5, 9, 12, 45) (this incorporation defect can be reversed by pseudotyping virions with heterologous Env glycoproteins containing short CTs or by removing the gp41 CT [9, 12, 26]), (ii) H…”

“In addition to its central role in promoting an interaction with the plasma membrane, other functions which have been attributed to the MA region of HIV-1 Pr55 include incorporation of the viral envelope protein onto the developing particle (12, 15, 40), an essential role in early postentry events of the viral life cy…”

“The ratio of apically to basolaterally releaseding of viral budding (Dorfman et al., 1994; Lodge et al., virions was similar to the levels obtained with envelope-1994). negative viruses.”

“MA, which has a crucial role in the incorporation of the viral surface glycoproteins (10, 52), remains associated with the host cell-derived lipid envelope of the virion (16).”

“MLV/HIV-p6 (lane 1), MLV/HIV-p6(1-41) (lane 2), and MLV/HIV-p6(1-46) or with the HIV-1 Gag polyprotein expression construct HXBH10-PR(2).”

“Although other retroviruses cannot be pseudotyped by full-length HIV-1 proteins, the MA domain of HIV-1 Gag is sufficient for the incorporation of full-length HIV-1 Env in particles produced from chimeric HIV-1–visna virus Gag proteins (8).”

“We reported previously that the HIV-1 capsidEnv glycoprotein interaction is very sensitive to alterations in the MA domain of the Gag polyprotein (9).”

“Without exception, substitutions and deletions in the p17 matrix protein previously shown to prevent the incorporation of Env glycoprotein (4) caused a nonpolarized distriVOL.”

“Consistent with this model, we previously reported that a small deletion termed D16-18, which removes a portion of helix 1 of MA, significantly increases particle assembly both at the plasma membrane and at intracellular membranes (12).”

“Since the Gag MA protein has been shown to be essential for envelope incorporation into particles (8, 39), it is conceivable that an aberrantly organized or folded p55 precursor could hinder the MA-Env interaction at the infected cell surface.”

“Second, incorporation of ICAM-1, unlike incorporation of the HIV-1 envelope glycoproteins, might not be constrained by interactions with viral matrix protein (13, 49).”

“MA is thought to play a central role in targeting the Gag precursor protein to the site of assembly on the plasma membrane (10, 41, 45, 52) and is essential for the stable association of the HIV-1 Env glycoprotein with the viral capsid (9, 45, 51).”

“…(Göttlinger et al. 1989 ) , directly mediates contacts between Gag and the plasma membrane (Spearman et al. 1994 ; Zhou et al. 1994 ) , and facilitates incorporation of the envelope proteins into the assembling virion (Yu et al. 1992 ; Dorfman et al. 1994 ; Freed and Martin 1995, 1996 ) (Fig.”

“A direct interaction between MA and Env CT in vitro has been reported [10] and there is strong genetic evidence supporting this interaction [5–8,18].”

“Finally, it will also be of interest to determine if a mutation at the analogous position in the HIV-1 TM cytoplasmic tail has a similar effect.”

“These and other results (14, 17, 74) suggested a direct interaction between MA and the long cytoplasmic tail of gp41.”

“Thus, the Gag precursor protein, which may interact with the cytoplasmic domain of gp41 during virus assembly (3, 8, 28, 31, 35, 49, 50), may prevent the internalization of the Env protein.”

“…(gp120/gp41) envelope (Env) protein trimers into virus particles (Yu et al., 1992; Wang and Barklis, 1993; Wang et al., 1993; Facke et al., 1993; Dorfman et al., 1994; Zhou et al., 1994; Mammano et al., 1995; Freed and Martin, 1995, 1996; Zhou and Resh, 1996; Ono et al., 1997, 2000; Ono and…”

“Immunorecognition of the Gag polyprotein by patient sera is frequently impaired even by minor alterations (6), which may explain why only relatively small amounts of the D126-277 Gag precursor were detected.”

“The full-length HIV-1 proviral constructs HXB-PR(2) (24) and HXB-gag(2) (16) are identical to the nef-negative HXBH10 infectious clone of HIV-1 (24), except for mutations that inactivate protease (PR) or prevent the expression of the Gag polyprotein Pr55.”

“precursor (49, 58), the viral envelope protein (13, 68), and the viral accessory protein Vpr (37, 38, 40, 50).”

“membrane association of Gag [73,79,80], while the latter is an important structural element involved in formation of the”

“MA has been postulated to be involved in a variety of steps in the HIV-1 life cycle, including the targeting and binding of the Gag precursor to the plasma membrane (37, 38), the incorporation of envelope (Env) glycoproteins into virions (5, 10, 11, 36), virus assembly and release (4, 12, 30, 32), and virus entry (29,…”

“To provide wild-type HIV-1 Env in trans, we used the mutant HIV-1 proviral clone HXBH10-gag(2) (4), which is unable to express internal struc* Corresponding author.”

“In addition to plasma membrane binding, the functional properties of Pr55 responsible for the production of an infectious virion include recruitment of the HIV-1 genome and specific viral proteins into budding virions and processing by HIV-1 protease to generate the structural proteins of the mature virus (8, 17, 18,…”

“It has been demonstrated that mutations in the matrix domain of the HIV-1 or the Mason-Pfizer monkey virus Gag precursor can impair inclusion of the respective viral spike proteins into virions (14, 43, 60), thereby strongly suggesting that core-spike interactions are needed for incorporation of spikes into virions.”

“The cytoplasmic tail of GP41 (GP41CT) not only enhances Env packaging during viral budding (77, 78) but also drives the rearrangements of Env prebundle structures during viral entry (79).”

“Mutations in the MA domain of HIV-1 Gag have been shown to disrupt interactions with the viral Env glycoproteins, leading to defects in Env incorporation into virions (14, 20, 21, 74) or impaired gp120-gp41 associations (9).”

“In contrast, a structure where the three MPER regions interact in a stalk might well be disrupted by the mutations we have introduced into this region, allowing the MPER to interact instead with the membrane through its tryptophan residues, which in turn could alter the ability of gp41 to interact with assembling Gag…”

“Incorporation of Env into virus particles is also dependent on the integrity of the MA domain (9, 60).”

“In the late stage of the viral life cycle, as part of the Pr55 Gag precursor, MA contributes sequences that are necessary for targeting the Gag precursor to the plasma membrane (3, 31, 39, 42) and for the incorporation, by the assembling virion, of the major surface glycoprotein gp160 (8, 11, 37, 38).”

“Several studies demonstrated that the HIV glycoproteins are incorporated into virus particles via an interaction with the Gag matrix (MA) domain (3, 9, 10, 13, 14, 24, 37).”

“Mutations within the MA protein can impair HIV-1 envelope incorporation (15, 23, 83).”

“Considering the sequence of the baculovirus polyhedrin and the evolutionary divergence between the HIV and HSRV genomes, these results suggested a certain degree of tolerance for Gag particle assembly and release at the N terminus of the HIV-1 Gag precursor, in terms of MA length and amino acid sequence (11).”

“following mutations: L8S plus S9R (MA-A), (16-18) (MA-B), W36S”

“cytoplasmic domain appears to influence the incorporation of glycoproteins into virions (13, 15, 16, 22, 25, 28, 39, 72, 73).”

“Matrix, a key component of the HIV-1 PIC, contributes to nuclear localization of the PIC and plays other crucial roles throughout the HIV-1 life cycle (6, 15, 24, 38, 50, 67).”

“To date, most of the studies concerning HIV-1 Env and Gag interaction have been performed with cells such as COS or HeLa cells, which are not the primary target cells of HIV-1 infection in vivo (3, 10, 38).”

“HIV-1 Env incorporation into budding virions is mediated by the matrix domain of the Gag polyprotein (Dorfman et al., 1994; Tedbury and Freed, 2014; Yu et al., 1992).”

“, 2000) and interaction with the p17 MA protein (Bukrinskaya & Sharova, 1990; Cosson, 1996; Dorfman et al., 1994; Freed & Martin, 1995a, b, 1996; Mammano et al., 1995; Murakami & Freed, 2000a; Wyma et al., 2000).”

“(ii) Direct Gag–Env interaction: Genetic data revealed that the MA domain of Gag is required for Env incorporation (Yu et al., 1992; Dorfman et al., 1994; Freed and Martin, 1995, 1996).”

“In this sort of arrangement, residues that have been identified genetically to interact with the HIV-1 transmembrane envelope protein (TM) and its cytoplasmic tail (12, 13, 16, 17, 59) are oriented towards threefold, clover leaf-shaped symmetric MyrMA lattice cage holes between hexamer units, rather than the hexamer h…”

“The results presented above show that the phenotype of the Y36S-L41P mutant is very similar to those of p17 mutants that have amino acid changes within the first 30 residues of MA (10, 11, 13, 62).”

“Indeed, this epitope is not invariant even for the B Clade (57), and amino acid changes in this region are tolerated and generate infectious virus (21,58).”