Insulin-Like Growth Factor II Receptor-Mediated Intracellular Retention of Cathepsin B Is Essential for Transformation of Endothelial Cells by Kaposi's Sarcoma-Associated Herpesvirus

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) is the pathological agent of Kaposi's sarcoma (KS),Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV8) belongs to the gammaherpesvirus subfamily and is the pathological agent of Kaposi's sarcoma (KS) and of lymphoproliferative disorders in B cells (20). KS is a mesenchymal tumor generally targeting the skin and soft tissue organs. The sarcoma is composed of interweaving bands of vascularizing spindle cells of endothelial origin, frequently associated with infiltrating inflammatory cells (8,35). AIDS has been most commonly associated with KS, although other forms of KS exist independently of human immunodeficiency virus infection, e.g., classic, endemic, and iatrogenic KS (15,35). Antiretroviral treatments against human immunodeficiency virus have effectively reduced the prevalence of AIDS-associated KS; however, the incidence of iatrogenic KS has increased 400% relative to the population growth in North America. This is most likely due to an increase in the number of organ transplant recipients (46).The development of several in vitro systems that rely on infection of primary or immortalized endothelial cells by KSHV has greatly advanced our understanding of virus-host cell interaction during tumorigenesis (31). Dermal microvascular endothelial cells stably transfected with the oncogenes E6 and E7 of human papillomavirus (E-DMVEC) are immortalized but remain contact inhibited, grow as discrete monolayers with a cobblestone phenotype, and enter senescence if not passaged after attaining confluence (37). Upon infection with KSHV, E-DMVEC develop a spindle cell phenotype, lose contact inhibition, form foci when cultured postconfluence, and acquire the ability to form colonies in soft agar (37). As in KS tumors, viral gene expression in E-DMVEC is largely restricted to open reading frame 71 (ORF71 [vFLIP]), ORF72 (vCyclin), ORF73 (latency-associated nuclear antigen [LANA]), and kaposin, and only a few cells spontaneously enter the lytic cycle of viral replication. Despite the restricted viral gene expression program, latent infections are associated with a dramatic reprogramming of the cellular transcriptome and proteome (4,38,39,55). Several virus-induced host cell proteins are required to support postconfluent growth, including c-Kit, hemoxygenase, RDC-1, Neuritin, and the insulin receptor (30,39,42,43).One of the hallmarks of KS is aberrant neoangiogenesis by proliferating spindle cells, resulting in abnormal vasculature. Neoangiogenesis involves the degradation of extracellular matrix by proteases, a process that frequently involves cysteine proteases of the cathepsin family (6,21,22,53). Despite this important role of cathepsins in many cancers, the role of cathepsin function in KS development has not been studied so far. Cathepsins are part of the papain subfamily within the cysteine protease superfamily. Most cathepsins are ubiquitously expressed in lysosomes and play a role in protein degradation and processing. In addition to these housekeep...

Propranolol Decreases Proliferation of Endothelial Cells Transformed by Kaposi's Sarcoma-Associated Herpesvirus and Induces Lytic Viral Gene Expression

“…Transduction of EC with the human papillomavirus E6 and E7 genes and infection with KSHV were performed as described previously (11). E6 and E7 allow for extended culture of EC without inducing a transformed phenotype; following infection with KSHV, however, E6/E7-expressing cells develop a fully transformed phenotype, including postconfluent and anchorage-independent growth (3,4,(11)(12)(13). The presence of E6 and E7 also allows for prolonged culture (in these experiments, 48 h) of EC in low-serum medium without recombinant growth factors, conditions that would otherwise induce apoptosis of other EC types due to growth factor withdrawal (14,15).…”

Discovery of Peptide Ligands for Hepatic Stellate Cells Using Phage Display

“…The sequences of IGF2R siRNA are 5′- UAUAGAGCAAGCCUGGUCU-3′ (sense strand) and 5′-AGACCAGGCUUGCUCUAUA-3′ (antisense strand) as reported. [24]…”

Most rotavirus strains require the cation-independent mannose-6-phosphate receptor, sortilin-1, and cathepsins to enter cells

“…The efficiency for silencing the expression of CI-M6PR and sortilin-1 by RNAi was determined by quantitative reverse transcription-PCR (qRT-PCR) as previously described (Ayala-Breton et al, 2009;Silva-Ayala et al, 2013). The forward primer 6333-F (5′-GCAGAAGCTGGG TGTCATAGG-3′) used to evaluate the CI-M6PR mRNA expression was previously described (Rose et al, 2007), while the sequence of the reverse primer was 5′-GTGCAGCTGTCGATATCAAACCTC-3′. The sequences of the forward and reverse primers used to evaluate the sortilin-1 mRNA expression levels were 5′-CTGGTCACAGTCGTAGCAGG-3′ and 5′-CAAGAGGTCCTCATCTGAGTCATC-3′, respectively.…”