Prolactin/growth hormone–derived antiangiogenic peptides highlight a potential role of tilted peptides in angiogenesis

Abstract

Angiogenesis is a crucial step in many pathologies, including tumor growth and metastasis. Here, we show that tilted peptides exert antiangiogenic activity. Tilted (or oblique-oriented) peptides are short peptides known to destabilize membranes and lipid cores and characterized by an asymmetric distribution of hydrophobic residues along the axis when helical. We have previously shown that 16-kDa fragments of the human prolactin͞growth hormone (PRL͞GH) family members are potent angiogenesis inhibitors. Here, we demonstrate that all these fragments possess a 14-aa sequence having the characteristics of a tilted peptide. The tilted peptides of human prolactin and human growth hormone induce endothelial cell apoptosis, inhibit endothelial cell proliferation, and inhibit capillary formation both in vitro and in vivo. These antiangiogenic effects are abolished when the peptides' hydrophobicity gradient is altered by mutation. We further demonstrate that the well known tilted peptides of simian immunodeficiency virus gp32 and Alzheimer's ␤-amyloid peptide are also angiogenesis inhibitors. Taken together, these results point to a potential new role for tilted peptides in regulating angiogenesis. 16-kDa N-terminal fragment of prolactinA ngiogenesis, the formation of new blood vessels from preexisting ones, is crucial in both health and disease. Its involvement in tumor growth and metastasis (1) makes it an important potential target for anticancer therapy. Many angiogenesis inhibitors are cryptic fragments of endogenous molecules displaying no angiogenesis-related activity [angiostatin, endostatin, platelet factor-4 (PF-4), tumstatin, and thrombospondin (2)]. From some of these inhibitors, shorter peptides retaining antiangiogenic activity have been isolated, such as the PF-4 peptide 47-70 (3), endostatin fragments 2 and 5 (amino acids 60-70 and amino acids 171-183) (4), and tumstatin peptides T3 and T7 (amino acids 69-88 and amino acids 74-98) (5). This observation suggests that the antiangiogenic regions of these peptides may be exposed in the isolated fragments but buried in the full-length proteins.The 16-kDa N-terminal fragment of prolactin (16K PRL) is antiangiogenic in vitro (6-11) and in vivo. Generation of the 16K fragment from PRL has been attributed to cathepsin D (12). Its ability to prevent angiogenesis in tumor and retinopathy mouse models has raised interest in its potential therapeutic use (13-15). We have sought to identify in human 16K PRL (16K hPRL) a peptide that might be responsible for its antiangiogenic activity. Although the 16K fragments of the other three human PRL͞GH-family members are also potently antiangiogenic (16), the sequence similarity of these fragments is low (Ϸ35% similarity between all mammalian PRL͞GH sequences). This consideration led us to seek a peculiar common structural feature rather than a similar sequence.Tilted (or oblique-oriented) peptides are short helical peptides (11 to 20 aa long) characterized by a peculiar distribution of hydrophobic residues: they are amphipathic ...

STAT5 and Prolactin Participate in a Positive Autocrine Feedback Loop That Promotes Angiogenesis

“…Although full-length PRL utilizes the PRLR, its proteolytic fragments appear to signal via a different receptor (39) or an alternative signaling mechanism that relies on the molecule's physical properties as "tilted" peptides (13). The existence of distinct signaling pathways of fulllength and 16-kDa forms of PRL is also supported by in vivo studies.…”

Inhibitory activity of the peptides derived from buffalo prolactin on angiogenesis

“…The hPRL and hGH tilted peptides (14-amino-acid sequence) consisting of 9 hydrophobic amino acids induce endothelial cell apoptosis and inhibit endothelial cell proliferation and capillary formation (Nguyen et al 2006). The tilted peptide has been known to destabilize membrane and lipid core and is characterized by an asymmetric distribution of hydrophobic residues along the axis when helical.…”

A systematic methodology for proteome-wide identification of peptides inhibiting the proliferation and migration of endothelial cells

“…For example, the thrombospondin 1 protein contains multiple thrombospondin type 1 (TSP1) domains, and short peptides contained within the second (Mal-2) and third (Mal-3) domains of the protein have been identified as antiangiogenic (3). The growth hormone (GH) and prolactin proteins contain the somatotropin-conserved domain, and short peptides derived from these domains have recently been identified as antiangiogenic (4). Pigment epithelium derived factor (PEDF) contains a serpin conserved domain, and short sequences within this domain have been recognized as the active antiangiogenic epitopes (5).…”