Reconstitution of the Ancestral Glycoprotein of Human Endogenous Retrovirus K and Modulation of Its Functional Activity by Truncation of the Cytoplasmic Domain

Hanke, Kirsten; Krämer, Philipp; Seeher, Sandra; Beimforde, Nadine; Kurth, Reinhard; Bannert, Norbert

doi:10.1128/jvi.01368-09

Cited by 41 publications

(61 citation statements)

References 54 publications

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“…It is interesting that, as previously seen for HERV-K113 Env (43), in the cell lysates we observe several HERV-K Env TM bands (e.g., Fig. 5, cell lysates), while only one of them is visible in the concentrated VLPs (Fig.…”

Section: Resultssupporting

confidence: 83%

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HIV-1 Interacts with Human Endogenous Retrovirus K (HML-2) Envelopes Derived from Human Primary Lymphocytes

Brinzevich

Young²,

Sebra

et al. 2014

J Virol

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Human endogenous retroviruses (HERVs) are viruses that have colonized the germ line and spread through vertical passage. Only the more recently acquired HERVs, such as the HERV-K (HML-2) group, maintain coding open reading frames. Expression of HERV-Ks has been linked to different pathological conditions, including HIV infection, but our knowledge on which specific HERV-Ks are expressed in primary lymphocytes currently is very limited. To identify the most expressed HERV-Ks in an unbiased manner, we analyzed their expression patterns in peripheral blood lymphocytes using Pacific Biosciences (PacBio) singlemolecule real-time (SMRT) sequencing. We observe that three HERV-Ks (KII, K102, and K18) constitute over 90% of the total HERV-K expression in primary human lymphocytes of five different donors. We also show experimentally that two of these HERV-K env sequences (K18 and K102) retain their ability to produce full-length and posttranslationally processed envelope proteins in cell culture. We show that HERV-K18 Env can be incorporated into HIV-1 but not simian immunodeficiency virus (SIV) particles. Moreover, HERV-K18 Env incorporation into HIV-1 virions is dependent on HIV-1 matrix. Taken together, we generated high-resolution HERV-K expression profiles specific for activated human lymphocytes. We found that one of the most abundantly expressed HERV-K envelopes not only makes a full-length protein but also specifically interacts with HIV-1. Our findings raise the possibility that these endogenous retroviral Env proteins could directly influence HIV-1 replication. IMPORTANCEHere, we report the HERV-K expression profile of primary lymphocytes from 5 different healthy donors. We used a novel deepsequencing technology (PacBio SMRT) that produces the long reads necessary to discriminate the complexity of HERV-K expression. We find that primary lymphocytes express up to 32 different HERV-K envelopes, and that at least two of the most expressed Env proteins retain their ability to make a protein. Importantly, one of them, the envelope glycoprotein of HERV-K18, is incorporated into HIV-1 in an HIV matrix-specific fashion. The ramifications of such interactions are discussed, as the possibility of HIV-1 target tissue broadening and immune evasion are considered.

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Section: Resultssupporting

confidence: 83%

“…It is also important to note that functional retroviral Env proteins have their precursor cleaved by cellular furin-like enzymes in the late Golgi apparatus (41,42) and that they are highly glycosylated (43,44), which results in the appearance of bands of different molecular weights (Fig. 4A).…”

Section: Resultsmentioning

confidence: 99%

HIV-1 Interacts with Human Endogenous Retrovirus K (HML-2) Envelopes Derived from Human Primary Lymphocytes

Brinzevich

Young²,

Sebra

et al. 2014

J Virol

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“…As controls, we designed two further variants that should block HERV-K-mediated fusion by engineering the predicted furin cleavage site, RSKR, to SSKS, yielding HERVK-CS Ϫ and HERVK ϩ -CS Ϫ , respectively (Fig. 1A) (15,46). To determine the effects of the modifications on HERV-K ENV expression, we transfected the respective plasmids into BSRT7 cells previously infected with a recombinant vaccinia virus expressing T7 RNA polymerase as a source of transcriptase.…”

Section: Resultsmentioning

confidence: 99%

“…The LatB insensitivity of VSV-HERVK ϩ contrasts with the LatB sensitivity of VSV and other VSV pseudotypes that depend upon clathrin-mediated endocytosis for their uptake, where the size of the particle dictates a need for the actin machinery to complete the process of internalization (48). To determine if dependence upon endosomal acidification and dynamin is specific to Bs-c-1 cells or whether it is a general requirement for HERV-K entry, we tested the sensitivity of VSV-HERVK ϩ to these inhibitors in CRFK cells, a feline kidney cell line that is known to support infection by viruses bearing HERV-K ENV (16,46). Bs-c-1 and CRFK cells were treated and infected with VSV-HERVK ϩ as described above, and eGFP expression was measured by flow cytometry (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Infectious Entry Pathway Mediated by the Human Endogenous Retrovirus K Envelope Protein

Robinson

Whelan

2016

J Virol

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Endogenous retroviruses (ERVs), the majority of which exist as degraded remnants of ancient viruses, comprise approximately 8% of the human genome. The youngest human ERVs (HERVs) belong to the HERV-K(HML-2) subgroup and were endogenized within the past 1 million years. The viral envelope protein (ENV) facilitates the earliest events of endogenization (cellular attachment and entry), and here, we characterize the requirements for HERV-K ENV to mediate infectious cell entry. Cell-cell fusion assays indicate that a minimum of two events are required for fusion, proteolytic processing by furin-like proteases and exposure to acidic pH. We generated an infectious autonomously replicating recombinant vesicular stomatitis virus (VSV) in which the glycoprotein was replaced by HERV-K ENV. HERV-K ENV imparts an endocytic entry pathway that requires dynamin-mediated membrane scission and endosomal acidification but is distinct from clathrin-dependent or macropinocytic uptake pathways. The lack of impediments to the replication of the VSV core in eukaryotic cells allowed us to broadly survey the HERV-K ENV-dictated tropism. Unlike extant betaretroviral envelopes, which impart a narrow species tropism, we found that HERV-K ENV mediates broad tropism encompassing cells from multiple mammalian and nonmammalian species. We conclude that HERV-K ENV dictates an evolutionarily conserved entry pathway and that the restriction of HERV-K to primate genomes reflects downstream stages of the viral replication cycle. IMPORTANCEApproximately 8% of the human genome is of retroviral origin. While many of those viral genomes have become inactivated, some copies of the most recently endogenized human retrovirus, HERV-K, can encode individual functional proteins. Here, we characterize the envelope protein (ENV) of the virus to define how it mediates infection of cells. We demonstrate that HERV-K ENV undergoes a proteolytic processing step and triggers membrane fusion in response to acidic pH-a strategy common to many viral fusogens. Our data suggest that the infectious entry pathway mediated by this ENV requires endosomal acidification and the GTPase dynamin but does not require clathrin-dependent uptake. In marked contrast to other betaretroviruses, HERV-K ENV imparts broad species tropism in cultured cells. This work provides new insights into the entry pathway of an extinct human virus and provides a powerful tool to further probe the endocytic route by which HERV-K infects cells. E ndogenous retroviruses (ERVs) comprise approximately 8% of the human genome (1). Such ERVs provide a physical record of ancient infections by once exogenous retroviruses; however, the degraded states of most sequences largely obscure their biological properties. Consequently, relatively little is known about the earliest events of endogenization, including how the viruses initially entered the germ line to become vertically transmitted elements. The process of endogenization begins with cellular attachment and viral entry, which is mediated by the envel...

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The Rec protein of HERV‐K(HML‐2) upregulates androgen receptor activity by binding to the human small glutamine‐rich tetratricopeptide repeat protein (hSGT)

Hanke

Chudak

Kurth

et al. 2012

Intl Journal of Cancer

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The expression of endogenous retroviruses of the HERV‐K(HML‐2) family is strongly upregulated in germ cell tumors and several other cancers. Although the accessory Rec protein of HERV‐K(HML‐2) has been shown to induce carcinoma in situ in transgenic mice, to increase the activity of c‐myc and to interact with the androgen receptor (AR), whether or not Rec expression is indeed implicated causally in the initiation or progression of any human malignancies remains unclear. We used the yeast two‐hybrid system involving the Rec protein of a recently integrated HERV‐K(HML‐2) element in an effort to identify potential Rec‐related oncogenic mechanisms. This revealed the human small glutamine‐rich tetratricopeptide repeat (TPR)‐containing protein (hSGT) to be a cellular binding partner. The interaction of Rec with this known negative regulator of the AR was confirmed by coimmunoprecipitation, pull‐down assays and colocalization studies. The interaction involves the TPR motif of hSGT and takes place in the cytoplasm and in the nucleoli. Using an AR‐responsive promoter and gene we could demonstrate that Rec interference with hSGT resulted in an up to five‐fold increase in the activity of AR. Furthermore, in AR positive cells, Rec was shown to act as transactivator by enhancing AR‐mediated activation of the HERV‐K(HML‐2) LTR promoter. This is in line with previous observations of elevated HERV‐K(HML‐2) expression in steroid‐regulated tissues. On the basis of our findings we propose a “vicious cycle” model of Rec‐driven hyperactivation of the AR leading to increased cell proliferation, inhibition of apoptosis and eventually to tumor induction or promotion.

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Reconstitution of the Ancestral Glycoprotein of Human Endogenous Retrovirus K and Modulation of Its Functional Activity by Truncation of the Cytoplasmic Domain

Cited by 41 publications

References 54 publications

HIV-1 Interacts with Human Endogenous Retrovirus K (HML-2) Envelopes Derived from Human Primary Lymphocytes

HIV-1 Interacts with Human Endogenous Retrovirus K (HML-2) Envelopes Derived from Human Primary Lymphocytes

Infectious Entry Pathway Mediated by the Human Endogenous Retrovirus K Envelope Protein

The Rec protein of HERV‐K(HML‐2) upregulates androgen receptor activity by binding to the human small glutamine‐rich tetratricopeptide repeat protein (hSGT)

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