Differentiating cells of murine stratified squamous epithelia constitutively express plasminogen activator inhibitor type 2 (PAI-2)

Risse, Barbara; Brown, Heather M.; Lavker, Robert M.; Pearson, Jay A.; Baker, Mark S.; Ginsburg, David; Jensen, Pamela J.

doi:10.1007/s004180050318

Cited by 26 publications

(24 citation statements)

References 47 publications

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“…How E6 and E7 oncoprotein-mediated inhibition of keratinocyte differentiation is overcome to allow later stages of the HPV viral life cycle is currently unclear (22). PAI-2 is absent in basal keratinocytes (35) but is a major product of differentiating keratinocytes (33,43). PAI-2 probably contributes to promoting keratinocyte differentiation by elevating Rb levels (45), and this might also lead to downregulation of episomal E6 and E7 transcription.…”

Section: Discussionmentioning

confidence: 99%

“…SerpinB2, originally described as plasminogen activator inhibitor type 2 (PAI-2), is expressed by a range of cell types including activated macrophages and many tumors and is a major product of differentiating squamous epithelial cells (33,43). PAI-2 was one of the first identified members of a unique and growing subclass of serine protease inhibitors (serpins) called ovalbumin-like serpins (ov-serpins) (49).…”

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confidence: 99%

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Silencing of Integrated Human Papillomavirus Type 18 Oncogene Transcription in Cells Expressing SerpinB2

Darnell

Antalis

Rose

et al. 2005

J Virol

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SerpinB2, originally described as plasminogen activator inhibitor type 2 (PAI-2), is expressed by a range of cell types including activated macrophages and many tumors and is a major product of differentiating squamous epithelial cells (33, 43). PAI-2 was one of the first identified members of a unique and growing subclass of serine protease inhibitors (serpins) called ovalbumin-like serpins (ov-serpins) (49). Ov-serpin family members often appear to have nucleocytoplasmic distributions (8, 15), and many have intracellular activities: for instance, CrmA and PI9 are involved in apoptosis inhibition, MENT is involved in DNA binding, and Maspin and Headapin are involved in tumor suppression (8, 49). Although extracellular PAI-2 is well documented as an inhibitor of the extracellular protease urokinase-type plasminogen activator (31), PAI-2 was recently shown to have an additional intracellular activity as a retinoblastoma protein (Rb) binding protein (15). PAI-2 was found to bind the C pocket of Rb via a novel binding motif called the PENF homology motif, which is present in the large C-D interhelical loop region of PAI-2. PAI-2 expression resulted in decreased Rb turnover, with the subsequent increase in Rb levels causing an increase in Rb-mediated activities. The PAI-2-mediated increase in Rb protein levels required both Rb binding via the C-D interhelical region of PAI-2 and an intact reactive site loop (RSL), which plays a pivotal role in the known protease inhibitory activity of PAI-2 (15). The new Rb-associated role for intracellular PAI-2 may explain why PAI-2 expression is often able to confer a series of Rb-related phenotypes such as resistance to apoptosis (19,23,61), regulation of gene transcription (1, 37, 48), promotion of differentiation (29,34,57), and tumor suppression (20,23,31,34,38,41,56).A dramatic phenotype resulting from stable PAI-2 expression in HeLa cells was recovery of Rb and loss of E7 protein levels in these human papillomavirus type 18 (HPV-18)-transformed cells (15). High-risk HPVs such as HPV-18 are often associated with cervical cancer (16), and cells from such cancers usually constitutively express the HPV oncoproteins E6 and E7 from HPV-derived DNA integrated into the host cell genome (36). E6 targets p53 and c-Myc, and E7

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Silencing of Integrated Human Papillomavirus Type 18 Oncogene Transcription in Cells Expressing SerpinB2

Darnell

Antalis

Rose

et al. 2005

J Virol

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“…High levels of PAI-2, which probably originate from the placenta, are present in late-pregnancy plasma (Kawano et al, 1968;Booth et al, 1988;Lecander and Astedt, 1986). Large quantities of PAI-2 are also found in human monocytes/macrophages (Wohlwend et al, 1987) and in human and mouse epidermis and various other murine stratified squamous epithelia (Hibino et al, 1988;Lyons-Giordano et al, 1994;Kawata et al, 1996;Risse et al, 1998). Two forms of PAI-2 have been described: a nonglycosylated form, which in many cell types is predominantly intracellular, and a glycosylated form, which at least in human mono-cytes/macrophages is secreted (Wohlwend et al, 1987).…”

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Evidence for intracellular cleavage of plasminogen activator inhibitor type 2 (PAI-2) in normal epidermal keratinocytes

et al. 2000

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Plasminogen activator inhibitor type 2 (PAI-2) is a serine proteinase inhibitor (serpin), present in high quantities in stratified squamous epithelia. Detergent extracts of human epidermis or cultured keratinocytes contain primarily active, nonglycosylated PAI-2. In keratinocytes, the vast majority of PAI-2 is retained within the cell, supporting the hypothesis that PAI-2 may serve specific intracellular function(s) through interaction with an unknown cytoplasmic proteinase. During interaction with the target proteinase, cleavage of PAI-2 within its reactive site loop leads to the formation of a more stable, "relaxed" conformation (PAI-2r). Using a monoclonal antibody specific for PAI-2r, we demonstrate here that PAI-2r is present in keratinocytes of the granular and basal layers of normal human epidermis. In addition, PAI-2r is detectable in cultured human epidermal keratinocytes, where it is concentrated in a detergent-insoluble fraction within differentiating cells. These data provide evidence for the presence of an endogenous, keratinocyte-derived proteinase that constitutively cleaves intracellular PAI-2 in normal human epidermal keratinocytes. Cleavage of PAI-2 by this proteinase may reflect specific intracellular action of PAI-2 in normal cells. Finally, we demonstrate that a commercially available anti-PAI-2 monoclonal antibody (#3750, American Diagnostica, Greenwich, CT), under native experimental conditions, preferentially recognizes the uncleaved, active form of PAI-2 and does not efficiently detect PAI-2r.

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“…It is expressed at high levels in the skin, hair follicles, gingival cells, the cervix, and placenta. PAI-2 is crosslinked to create the cornified envelope in terminally differentiated epithelial cells, where it forms a proteinaceous coat, with PAI-2 in both the active and relaxed forms (11,12).PAI-2 appears to have several distinct biological functions (10). To date, complexes between PAI-2 and uPA have not been observed in vivo.…”

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Crystal Structure of the Complex of Plasminogen Activator Inhibitor 2 with a Peptide Mimicking the Reactive Center Loop

Jankova¹,

Harrop²,

Saunders³

et al. 2001

Journal of Biological Chemistry

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The structure of the serpin, plasminogen activator inhibitor type-2 (PAI-2), in a complex with a peptide mimicking its reactive center loop (RCL) has been determined at 1.6-Å resolution. The structure shows the relaxed state serpin structure with a prominent sixstranded ␤-sheet. Clear electron density is seen for all residues in the peptide. The P1 residue of the peptide binds to a well defined pocket at the base of PAI-2 that may be important in determining the specificity of protease inhibition. The stressed-to-relaxed state (S 3 R) transition in PAI-2 can be modeled as the relative motion between a quasirigid core domain and a smaller segment comprising helix hF and ␤-strands s1A, s2A, and s3A. A comparison of the Ramachandran plots of the stressed and relaxed state PAI-2 structures reveals the location of several hinge regions connecting these two domains. The hinge regions cluster in three locations on the structure, ensuring a cooperative S 3 R transition. We hypothesize that the hinge formed by the conserved Gly 206 on ␤-strand s3A in the breach region of PAI-2 effects the S 3 R transition by altering its backbone torsion angles. This torsional change is due to the binding of the P14 threonine of the RCL to the open breach region of PAI-2.The serpins are an unusual class of protein in that they fold into a metastable structure (the stressed state) that can usually undergo a major structural change to an extremely stable form (the relaxed state) on cleavage by a target protease (1). Most serpins are serine (or cysteine) protease inhibitors that act in a suicide fashion, using the stability of the relaxed state to trap the protease in a nonfunctional covalent serpin-protease complex. The target protease cuts the accessible reactive center loop (RCL) 1 on the serpin to produce a covalent acyl intermediate (2, 3). The RCL then inserts into ␤-sheet 2 A to form the relaxed state. Attached to the RCL, the target protease moves to the base of the serpin, where it is partially unfolded, thus inhibiting its activity (4, 5). This mode of action, whereby one protein uses the increased stability of an altered conformer to partially unfold a second, covalently bound target protein, is unprecedented in biology.Plasminogen activator inhibitor 2 (PAI-2) is a serine protease inhibitor that belongs to the ov-serpin branch of the serpin superfamily (6). PAI-2 is an effective inhibitor of urinary plasminogen activator (urokinase or uPA) and, to a lesser extent, an inhibitor of tissue-type plasminogen activator. PAI-2 has several features that distinguish it from the more widely studied serpins. PAI-2 lacks an N-terminal secretory signal but contains a relatively inefficient internal signal sequence (7). This produces a distribution where a majority (ϳ70%) of the protein is nonglycosylated and intracellular, with the rest in a glycosylated, extracellular form. PAI-2 has a unique insertion of ϳ30 residues between helices hC and hD (CD loop), which is the site of glycosylation and the site of cross-linking to the cell membrane a...

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Differentiating cells of murine stratified squamous epithelia constitutively express plasminogen activator inhibitor type 2 (PAI-2)

Cited by 26 publications

References 47 publications

Silencing of Integrated Human Papillomavirus Type 18 Oncogene Transcription in Cells Expressing SerpinB2

Silencing of Integrated Human Papillomavirus Type 18 Oncogene Transcription in Cells Expressing SerpinB2

Evidence for intracellular cleavage of plasminogen activator inhibitor type 2 (PAI-2) in normal epidermal keratinocytes

Crystal Structure of the Complex of Plasminogen Activator Inhibitor 2 with a Peptide Mimicking the Reactive Center Loop

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