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Two Faces of Cathepsin D: Physiological Guardian Angel and Pathological Demon.

Khalkhali-Ellis Z, Hendrix MJ - Biol Med (Aligarh) (2014)

Bottom Line: Specifically, deregulated synthesis, post-translational modifications and hyper-secretion of CatD, along with its mitogenic effects, are established hallmarks of cancer.This review outlines CatD's post-translational modifications, cellular trafficking, secretion and protein binding partners in normal mammary gland, and restates the "site-specific" function of CatD which is most probably dictated by its post-translational modifications and binding partners.Noteworthy, CatD's association with one of its binding partners in the context of drug sensitivity is highlighted, with the optimism that it could contribute to the development of more effective chemotherapeutic agent(s) tailored for individual patients.

View Article: PubMed Central - PubMed

Affiliation: Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine, 2300 Children's Plaza, Box 222, Chicago, Illinois, 60614-3394, USA.

ABSTRACT

Since its discovery as a lysosomal hydrolase, Cathepsin D (CatD) has been the subject of intensive scrutiny by numerous scientists. Those accumulated efforts have defined its biosynthetic pathway, structure, and companion proteins in the context of its perceived "house keeping" function. However, in the past two decades CatD has emerged as a multifunctional enzyme, involved in myriad biological processes beyond its original "housekeeping" role. CatD is responsible for selective and limited cleavage (quite distinct from non-specific protein degradation) of particular substrates vital to proper cellular function. These proteolytic events are critical in the control of biological processes, including cell cycle progression, differentiation and migration, morphogenesis and tissue remodeling, immunological processes, ovulation, fertilization, neuronal outgrowth, angiogenesis, and apoptosis. Consistent with the biological relevance of CatD, its deficiency, altered regulation or post-translational modification underlie important pathological conditions such as cancer, atherosclerosis, neurological and skin disorders. Specifically, deregulated synthesis, post-translational modifications and hyper-secretion of CatD, along with its mitogenic effects, are established hallmarks of cancer. More importantly, but less studied, is its significance in regulating the sensitivity to anticancer drugs. This review outlines CatD's post-translational modifications, cellular trafficking, secretion and protein binding partners in normal mammary gland, and restates the "site-specific" function of CatD which is most probably dictated by its post-translational modifications and binding partners. Noteworthy, CatD's association with one of its binding partners in the context of drug sensitivity is highlighted, with the optimism that it could contribute to the development of more effective chemotherapeutic agent(s) tailored for individual patients.

No MeSH data available.


Related in: MedlinePlus

CatD cleavage products and N-glycan structures in normal mammary epithelial cells (HMEpCs) compared to breast cancer cell lines MCF-7 and MDA-MB231. Cytosolic fractions (25 μg total protein), and conditioned media (CM) from HMEpCs and breast cancer cell lines MCF-7 and MDA-MB231 were treated with or without endoglycosidase H (Endo-H, to remove the chitobiose core of high mannose and some hybrid oligosaccharides), and peptide-N-glycosidase F (PGNase, to remove high mannose, hybrid and complex glycans), then subjected to SDS-PAGE (10% acrylamide gel) and Western blot analysis. CM from the three cell lines was concentrated prior to treatment (HMEpC: 35×, MCF-7 and MDA-MB231: 2×). Differences in the abundance of the processed forms (A), and the N-glycan moieties of CatD (B&C), between normal mammary epithelial cells and breast cancer cell lines are evident in these Western blots. Note the preferential presence of multiple high mannose N-glycan structures (indicated by the appearance of multiple bands following Endo-H treatment) of the CM from the cancer cell lines.
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Figure 2: CatD cleavage products and N-glycan structures in normal mammary epithelial cells (HMEpCs) compared to breast cancer cell lines MCF-7 and MDA-MB231. Cytosolic fractions (25 μg total protein), and conditioned media (CM) from HMEpCs and breast cancer cell lines MCF-7 and MDA-MB231 were treated with or without endoglycosidase H (Endo-H, to remove the chitobiose core of high mannose and some hybrid oligosaccharides), and peptide-N-glycosidase F (PGNase, to remove high mannose, hybrid and complex glycans), then subjected to SDS-PAGE (10% acrylamide gel) and Western blot analysis. CM from the three cell lines was concentrated prior to treatment (HMEpC: 35×, MCF-7 and MDA-MB231: 2×). Differences in the abundance of the processed forms (A), and the N-glycan moieties of CatD (B&C), between normal mammary epithelial cells and breast cancer cell lines are evident in these Western blots. Note the preferential presence of multiple high mannose N-glycan structures (indicated by the appearance of multiple bands following Endo-H treatment) of the CM from the cancer cell lines.

Mentions: Conversion of the pre-pro-CatD to the active two-chain enzyme is a non-reversible process encompassing consecutive and highly regulated proteolytic steps [41,42]. Initially, the pre-peptide (20 amino acids), and the pro-peptide (44 amino acids) are sequentially removed to form the 48 kDa single-chain molecule [21,43]. Next, seven amino acids of the single chain’s NH2-terminus are removed by unidentified endo- and amino-peptidases, followed by removal of the sequence Ser-Ala-Ser-Ser-Ala-Ser-Ala-Leu (position 97–105). This modified single chain enzyme is cleaved by cysteine endopeptidase(s) to two chains, which undergo further processing to yield the active light and heavy chain CatD (Figure 1B). The significance of these precise proteolytic cleavages has eluded scientists, and with the increasing list of CatD functions, specifically during development and in embryonic stages, it is tempting to speculate that “functional specificity” tightly regulates the generation of CatD cleavage products. In this context, our laboratory has reported the differential processing of CatD during mammary gland development and remodeling (Figure 1C) [30]. These studies were first to demonstrate the plasticity of mammary tissue with respect to CatD production, proteolytic cleavage and activity. Notably, quiescent, non-lactating mammary epithelial cells have low constitutive levels of CatD in the pro-, single chain and two chain active enzyme format. At lactation, CatD’s cleavage profile remains comparable to non-lactating gland, while a considerable level of pro-CatD is apically released into the lumen. The level and apical release of pro-CatD diminishes considerably as lactation progresses. At the onset of involution, CatD is tyrosine nitrated [43], its processing is halted at the single chain active enzyme form [30] (Figure 1C). The generation of the mature two-chain active enzyme is resumed after 48h and peaks at days 3–4 of involution. In depth analysis of signals directing these proteolytic processes could unravel the specific regulatory checkpoints that have gone awry in cancer. Comparison of CatD production and processing profiles of normal mammary epithelial cells and breast cancer cell lines MCF-7 and MDA-MB231 indicates dramatic increase in the production, differences in the apparent molecular mass and level of the single chain form in the latter two cell lines (Figure 2A, Khalkhali-Ellis, unpublished observations). Specifically, pro-CatD secretion in cancer cell lines is ~30–40 folds higher than that of normal mammary epithelial cells, which further confirms the reported studies of delayed processing, accumulation of the 52 and 48 kDa forms, and secretion of over 50% of the pro-CatD in majority of cancer cell lines [12, 44].


Two Faces of Cathepsin D: Physiological Guardian Angel and Pathological Demon.

Khalkhali-Ellis Z, Hendrix MJ - Biol Med (Aligarh) (2014)

CatD cleavage products and N-glycan structures in normal mammary epithelial cells (HMEpCs) compared to breast cancer cell lines MCF-7 and MDA-MB231. Cytosolic fractions (25 μg total protein), and conditioned media (CM) from HMEpCs and breast cancer cell lines MCF-7 and MDA-MB231 were treated with or without endoglycosidase H (Endo-H, to remove the chitobiose core of high mannose and some hybrid oligosaccharides), and peptide-N-glycosidase F (PGNase, to remove high mannose, hybrid and complex glycans), then subjected to SDS-PAGE (10% acrylamide gel) and Western blot analysis. CM from the three cell lines was concentrated prior to treatment (HMEpC: 35×, MCF-7 and MDA-MB231: 2×). Differences in the abundance of the processed forms (A), and the N-glycan moieties of CatD (B&C), between normal mammary epithelial cells and breast cancer cell lines are evident in these Western blots. Note the preferential presence of multiple high mannose N-glycan structures (indicated by the appearance of multiple bands following Endo-H treatment) of the CM from the cancer cell lines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4318633&req=5

Figure 2: CatD cleavage products and N-glycan structures in normal mammary epithelial cells (HMEpCs) compared to breast cancer cell lines MCF-7 and MDA-MB231. Cytosolic fractions (25 μg total protein), and conditioned media (CM) from HMEpCs and breast cancer cell lines MCF-7 and MDA-MB231 were treated with or without endoglycosidase H (Endo-H, to remove the chitobiose core of high mannose and some hybrid oligosaccharides), and peptide-N-glycosidase F (PGNase, to remove high mannose, hybrid and complex glycans), then subjected to SDS-PAGE (10% acrylamide gel) and Western blot analysis. CM from the three cell lines was concentrated prior to treatment (HMEpC: 35×, MCF-7 and MDA-MB231: 2×). Differences in the abundance of the processed forms (A), and the N-glycan moieties of CatD (B&C), between normal mammary epithelial cells and breast cancer cell lines are evident in these Western blots. Note the preferential presence of multiple high mannose N-glycan structures (indicated by the appearance of multiple bands following Endo-H treatment) of the CM from the cancer cell lines.
Mentions: Conversion of the pre-pro-CatD to the active two-chain enzyme is a non-reversible process encompassing consecutive and highly regulated proteolytic steps [41,42]. Initially, the pre-peptide (20 amino acids), and the pro-peptide (44 amino acids) are sequentially removed to form the 48 kDa single-chain molecule [21,43]. Next, seven amino acids of the single chain’s NH2-terminus are removed by unidentified endo- and amino-peptidases, followed by removal of the sequence Ser-Ala-Ser-Ser-Ala-Ser-Ala-Leu (position 97–105). This modified single chain enzyme is cleaved by cysteine endopeptidase(s) to two chains, which undergo further processing to yield the active light and heavy chain CatD (Figure 1B). The significance of these precise proteolytic cleavages has eluded scientists, and with the increasing list of CatD functions, specifically during development and in embryonic stages, it is tempting to speculate that “functional specificity” tightly regulates the generation of CatD cleavage products. In this context, our laboratory has reported the differential processing of CatD during mammary gland development and remodeling (Figure 1C) [30]. These studies were first to demonstrate the plasticity of mammary tissue with respect to CatD production, proteolytic cleavage and activity. Notably, quiescent, non-lactating mammary epithelial cells have low constitutive levels of CatD in the pro-, single chain and two chain active enzyme format. At lactation, CatD’s cleavage profile remains comparable to non-lactating gland, while a considerable level of pro-CatD is apically released into the lumen. The level and apical release of pro-CatD diminishes considerably as lactation progresses. At the onset of involution, CatD is tyrosine nitrated [43], its processing is halted at the single chain active enzyme form [30] (Figure 1C). The generation of the mature two-chain active enzyme is resumed after 48h and peaks at days 3–4 of involution. In depth analysis of signals directing these proteolytic processes could unravel the specific regulatory checkpoints that have gone awry in cancer. Comparison of CatD production and processing profiles of normal mammary epithelial cells and breast cancer cell lines MCF-7 and MDA-MB231 indicates dramatic increase in the production, differences in the apparent molecular mass and level of the single chain form in the latter two cell lines (Figure 2A, Khalkhali-Ellis, unpublished observations). Specifically, pro-CatD secretion in cancer cell lines is ~30–40 folds higher than that of normal mammary epithelial cells, which further confirms the reported studies of delayed processing, accumulation of the 52 and 48 kDa forms, and secretion of over 50% of the pro-CatD in majority of cancer cell lines [12, 44].

Bottom Line: Specifically, deregulated synthesis, post-translational modifications and hyper-secretion of CatD, along with its mitogenic effects, are established hallmarks of cancer.This review outlines CatD's post-translational modifications, cellular trafficking, secretion and protein binding partners in normal mammary gland, and restates the "site-specific" function of CatD which is most probably dictated by its post-translational modifications and binding partners.Noteworthy, CatD's association with one of its binding partners in the context of drug sensitivity is highlighted, with the optimism that it could contribute to the development of more effective chemotherapeutic agent(s) tailored for individual patients.

View Article: PubMed Central - PubMed

Affiliation: Stanley Manne Children's Research Institute, Northwestern University Feinberg School of Medicine, 2300 Children's Plaza, Box 222, Chicago, Illinois, 60614-3394, USA.

ABSTRACT

Since its discovery as a lysosomal hydrolase, Cathepsin D (CatD) has been the subject of intensive scrutiny by numerous scientists. Those accumulated efforts have defined its biosynthetic pathway, structure, and companion proteins in the context of its perceived "house keeping" function. However, in the past two decades CatD has emerged as a multifunctional enzyme, involved in myriad biological processes beyond its original "housekeeping" role. CatD is responsible for selective and limited cleavage (quite distinct from non-specific protein degradation) of particular substrates vital to proper cellular function. These proteolytic events are critical in the control of biological processes, including cell cycle progression, differentiation and migration, morphogenesis and tissue remodeling, immunological processes, ovulation, fertilization, neuronal outgrowth, angiogenesis, and apoptosis. Consistent with the biological relevance of CatD, its deficiency, altered regulation or post-translational modification underlie important pathological conditions such as cancer, atherosclerosis, neurological and skin disorders. Specifically, deregulated synthesis, post-translational modifications and hyper-secretion of CatD, along with its mitogenic effects, are established hallmarks of cancer. More importantly, but less studied, is its significance in regulating the sensitivity to anticancer drugs. This review outlines CatD's post-translational modifications, cellular trafficking, secretion and protein binding partners in normal mammary gland, and restates the "site-specific" function of CatD which is most probably dictated by its post-translational modifications and binding partners. Noteworthy, CatD's association with one of its binding partners in the context of drug sensitivity is highlighted, with the optimism that it could contribute to the development of more effective chemotherapeutic agent(s) tailored for individual patients.

No MeSH data available.


Related in: MedlinePlus