Biomedical subjects

Thomas W Hodge

Publications and source records attributed to Thomas W Hodge.

6 recordsLinked to original sources

PubMed2006

Internalized Pseudomonas exotoxin A can exploit multiple pathways to reach the endoplasmic reticulum.

Receptor-mediated internalization to the endoplasmic reticulum (ER) and subsequent retro-translocation to the cytosol are essential sequential processes required for the intoxication of mammalian cells by Pseudomonas exotoxin A (PEx). The toxin binds the alpha2-macroglobulin receptor/low-density lipoprotein receptor-related protein. Here, we show that in HeLa cells, PEx recruits a proportion of this receptor to detergent-resistant microdomains (DRMs). Uptake of receptor-bound PEx involves transport steps both directly from early endosomes to the trans-Golgi network (TGN) independently of Rab9 function and from late endosomes to the TGN in a Rab9-dependent manner. Furthermore, treatments that simultaneously perturb both Arf1-dependent and Rab6-dependent retrograde pathways show that PEx can use multiple routes to reach the ER. The Rab6-dependent route has only been described previously for cargo with lipid-sorting signals. These findings suggest that partial localization of PEx within DRM permits a choice of trafficking routes consistent with a model that DRM-associated toxins reach the ER on a lipid-dependent sorting pathway whilst non-DRM-associated PEx exploits the previously characterized KDEL receptor-mediated uptake pathway. Thus, unexpectedly, an ER-directed toxin with a proteinaceous receptor shows promiscuity in its intracellular trafficking pathways, exploiting routes controlled by both lipid- and protein-sorting signals.

3T3 Cells↗

PubMed2005

Rab9 GTPase is required for replication of human immunodeficiency virus type 1, filoviruses, and measles virus.

Rab proteins and their effectors facilitate vesicular transport by tethering donor vesicles to their respective target membranes. By using gene trap insertional mutagenesis, we identified Rab9, which mediates late-endosome-to-trans-Golgi-network trafficking, among several candidate host genes whose disruption allowed the survival of Marburg virus-infected cells, suggesting that Rab9 is utilized in Marburg replication. Although Rab9 has not been implicated in human immunodeficiency virus (HIV) replication, previous reports suggested that the late endosome is an initiation site for HIV assembly and that TIP47-dependent trafficking out of the late endosome to the trans-Golgi network facilitates the sorting of HIV Env into virions budding at the plasma membrane. We examined the role of Rab9 in the life cycles of HIV and several unrelated viruses, using small interfering RNA (siRNA) to silence Rab9 expression before viral infection. Silencing Rab9 expression dramatically inhibited HIV replication, as did silencing the host genes encoding TIP47, p40, and PIKfyve, which also facilitate late-endosome-to-trans-Golgi vesicular transport. In addition, silencing studies revealed that HIV replication was dependent on the expression of Rab11A, which mediates trans-Golgi-to-plasma-membrane transport, and that increased HIV Gag was sequestered in a CD63+ endocytic compartment in a cell line stably expressing Rab9 siRNA. Replication of the enveloped Ebola, Marburg, and measles viruses was inhibited with Rab9 siRNA, although the non-enveloped reovirus was insensitive to Rab9 silencing. These results suggest that Rab9 is an important cellular target for inhibiting diverse viruses and help to define a late-endosome-to-plasma-membrane vesicular transport pathway important in viral assembly.

Animals↗

PubMed2004

Frequent human leukocyte antigen class I alleles are associated with higher viral load among HIV type 1 seroconverters in Thailand.

The loss of viral control by the host may be due to the evolution of viruses with mutations that limit presentation by human leukocyte antigen (HLA) to cytotoxic T cells. The authors hypothesized that the consequence of such evolution might be that persons with common HLA class I alleles would be less able to control viremia, on average, than would those with rare alleles. HLA class I typing was completed for 128 injection drug users who seroconverted in a prospective cohort study in Bangkok, Thailand. Logistic regression was used to model viral load (greater than or equal to the median) at 9 and 12 months after seroconversion with an HLA score that profiled the relative prevalence of each individual's alleles. At 12 months after seroconversion, injection drug users with the most common HLA alleles (highest quartile HLA score) had an almost 4-fold increased risk for higher viral load (> or = 32,055 copies/mL) than injection drug users with less common HLA alleles (adjusted odds ratio, 3.92; 95% confidence interval, 1.3-11.8). These findings support the importance of frequency-dependent effects of host genes on HIV type 1 evolution in different populations and suggest that HLA-driven viral evolution critically influences control of viremia in early HIV type 1 infection.

Alleles↗

PubMed2004

High resolution crystal structure of human Rab9 GTPase: a novel antiviral drug target.

Rab GTPases and their effectors facilitate vesicular transport by tethering donor vesicles to their respective target membranes. Rab9 mediates late endosome to trans-Golgi transport and has recently been found to be a key cellular component for human immunodeficiency virus-1, Ebola, Marburg, and measles virus replication, suggesting that it may be a novel target in the development of broad spectrum antiviral drugs. As part of our structure-based drug design program, we have determined the crystal structure of a C-terminally truncated human Rab9 (residues 1-177) to 1.25-A resolution. The overall structure shows a characteristic nucleotide binding fold consisting of a six-stranded beta-sheet surrounded by five alpha-helices with a tightly bound GDP molecule in the active site. Structure-based sequence alignment of Rab9 with other Rab proteins reveals that its active site consists of residues highly conserved in the Rab GTPase family, implying a common catalytic mechanism. However, Rab9 contains seven regions that are significantly different in conformation from other Rab proteins. Some of those regions coincide with putative effector-binding sites and switch I and switch II regions identified by structure/sequence alignments. The Rab9 structure at near atomic resolution provides an excellent model for structure-based antiviral drug design.

Amino Acid Sequence↗

PubMed2003

Broad human immunodeficiency virus (HIV)-specific T cell responses to conserved HIV proteins in HIV-seronegative women highly exposed to a single HIV-infected partner.

Eighteen highly exposed but persistently seronegative (HEPS) women (HW) and their human immunodeficiency virus (HIV) type 1-seropositive male partners were studied for HIV-specific T cells and other host factors. Circulating HIV-specific T cells were measured by interferon-gamma enzyme-linked immunospot assays, using recombinant vaccinia virus vectors expressing HIV proteins. Nine (50%) of the HW and all HIV-seropositive persons had HIV-specific T cell responses. Only 2 (22%) of the HEPS responders recognized Env, compared with 94% of HIV-seropositive persons. A high percentage (75%) of the HW with HIV-specific T cell responses reported recent HIV exposure. Remarkably, however, long-lived HIV-specific T cells were detected in 2 HW who had an extended period (>3.9 years) of no HIV exposure. These findings have important implications for HIV vaccine design.

AIDS Vaccines↗

PubMed2002

Discordance at human leukocyte antigen-DRB3 and protection from human immunodeficiency virus type 1 transmission.

Host human leukocyte antigens (HLAs) integrated into the human immunodeficiency virus (HIV) type 1 envelope could theoretically determine, as in tissue transplants, whether HIV-1 is "rejected" by exposed susceptible persons, preventing transmission. HLA discordance (mismatch) was examined among 45 heterosexual partner pairs in which at least 1 partner was HIV-1 infected and exposure or transmission between partners had occurred. Immunologic discordance at class II HLA-DRB3 (present in the HIV donor partner but absent in the recipient partner) was associated with lack of transmission of HIV-1. Eight (35%) of 23 partner pairs in which HIV-1 transmission did not occur were immunologically discordant at HLA-DRB3, compared with 0 of 11 partner pairs in which HIV-1 transmission did occur (P=.027). Further investigation of the roles of class II HLAs in HIV-1 transmission and as possible components of HIV-1 vaccines should be pursued.

Adult↗