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CXCR7 protein expression in human adult brain and differentiated neurons.

Shimizu S, Brown M, Sengupta R, Penfold ME, Meucci O - PLoS ONE (2011)

Bottom Line: Furthermore, confocal microscopy and binding assays in cultured neurons show that CXCR7 protein is mainly located into cytoplasm, while little to no protein expression is found on neuronal plasma membrane.Interestingly, specific CXCR7 ligands that inhibit CXCL12 binding to CXCR7 do not alter CXCR4-activated survival signaling (pERK/pAkt) in rat cortical neurons.Overall, these results implicate CXCR4 as the main CXCL12 signaling receptor on the surface of differentiated neurons and suggest that CXCR7 may interact with CXCR4 at the intracellular level, possibly affecting CXCR4 trafficking and/or coupling to other proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT

Background: CXCR7 and CXCR4 are receptors for the chemokine CXCL12, which is involved in essential functions of the immune and nervous systems. Although CXCR7 transcripts are widely expressed throughout the central nervous system, little is known about its protein distribution and function in the adult brain. To evaluate its potential involvement in CXCL12/CXCR4 signaling in differentiated neurons, we studied CXCR7 protein expression in human brain and cultured neurons.

Methodology/principal findings: Immunohistochemistry and RT-PCR analyses of cortex and hippocampus from control and HIV-positive subjects provided the first evidence of CXCR7 protein expression in human adult neurons, under normal and pathological conditions. Furthermore, confocal microscopy and binding assays in cultured neurons show that CXCR7 protein is mainly located into cytoplasm, while little to no protein expression is found on neuronal plasma membrane. Interestingly, specific CXCR7 ligands that inhibit CXCL12 binding to CXCR7 do not alter CXCR4-activated survival signaling (pERK/pAkt) in rat cortical neurons. Neuronal CXCR7 co-localizes to some extent with the endoplasmic reticulum marker ERp29, but not with early/late endosome markers. Additionally, large areas of overlap are detected in the intracellular pattern of CXCR7 and CXCR4 expression.

Conclusions/significance: Overall, these results implicate CXCR4 as the main CXCL12 signaling receptor on the surface of differentiated neurons and suggest that CXCR7 may interact with CXCR4 at the intracellular level, possibly affecting CXCR4 trafficking and/or coupling to other proteins.

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Related in: MedlinePlus

Staining of breast carcinoma with the CXCR7 antibody 11G8.A tissue array, containing samples from infiltrating ductal carcinoma and                            normal breast tissue, was stained to examine CXCR7 expression using the                            monoclonal antibody 11G8 (10 µg/mL)-as described in the methods.                            Representative images from infiltrating ductal carcinoma or normal                            tissue are shown here. Adjacent sections of the same samples were                            stained with Hematoxylin and Eosin (H&E) or the isotype (i.e. mouse                            IgG1) control, as indicated for each panel. (A/B/C) Infiltrating ductal                            carcinoma (NC = isotype control). (D/E) Normal                            breast tissue. (A2, B2, E2) High magnification of black squares in A, B,                            and E, respectively. Scale bars: 400 µm (A–E), 100 µm                            (A2, B2, E2).
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pone-0020680-g001: Staining of breast carcinoma with the CXCR7 antibody 11G8.A tissue array, containing samples from infiltrating ductal carcinoma and normal breast tissue, was stained to examine CXCR7 expression using the monoclonal antibody 11G8 (10 µg/mL)-as described in the methods. Representative images from infiltrating ductal carcinoma or normal tissue are shown here. Adjacent sections of the same samples were stained with Hematoxylin and Eosin (H&E) or the isotype (i.e. mouse IgG1) control, as indicated for each panel. (A/B/C) Infiltrating ductal carcinoma (NC = isotype control). (D/E) Normal breast tissue. (A2, B2, E2) High magnification of black squares in A, B, and E, respectively. Scale bars: 400 µm (A–E), 100 µm (A2, B2, E2).

Mentions: Previous studies have demonstrated that CXCR7 protein is specifically expressed in human breast cancer as opposed to normal breast tissue [27]. Therefore, our first step consisted in testing our staining protocol with the 11G8 antibody using a human tissue microarray that contained normal breast tissue and multiple breast carcinomas on the same slide. As expected, CXCR7 was expressed in most of the carcinomas but not in normal breast tissue. Two examples are reported in Figure 1 (A/D). This figure also shows the typical alterations of the glandular structure in the cancer tissue as compared to normal (counterstaining in 1B/E), higher magnification images of selected areas (square insets), and a negative control (1C).


CXCR7 protein expression in human adult brain and differentiated neurons.

Shimizu S, Brown M, Sengupta R, Penfold ME, Meucci O - PLoS ONE (2011)

Staining of breast carcinoma with the CXCR7 antibody 11G8.A tissue array, containing samples from infiltrating ductal carcinoma and                            normal breast tissue, was stained to examine CXCR7 expression using the                            monoclonal antibody 11G8 (10 µg/mL)-as described in the methods.                            Representative images from infiltrating ductal carcinoma or normal                            tissue are shown here. Adjacent sections of the same samples were                            stained with Hematoxylin and Eosin (H&E) or the isotype (i.e. mouse                            IgG1) control, as indicated for each panel. (A/B/C) Infiltrating ductal                            carcinoma (NC = isotype control). (D/E) Normal                            breast tissue. (A2, B2, E2) High magnification of black squares in A, B,                            and E, respectively. Scale bars: 400 µm (A–E), 100 µm                            (A2, B2, E2).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3105114&req=5

pone-0020680-g001: Staining of breast carcinoma with the CXCR7 antibody 11G8.A tissue array, containing samples from infiltrating ductal carcinoma and normal breast tissue, was stained to examine CXCR7 expression using the monoclonal antibody 11G8 (10 µg/mL)-as described in the methods. Representative images from infiltrating ductal carcinoma or normal tissue are shown here. Adjacent sections of the same samples were stained with Hematoxylin and Eosin (H&E) or the isotype (i.e. mouse IgG1) control, as indicated for each panel. (A/B/C) Infiltrating ductal carcinoma (NC = isotype control). (D/E) Normal breast tissue. (A2, B2, E2) High magnification of black squares in A, B, and E, respectively. Scale bars: 400 µm (A–E), 100 µm (A2, B2, E2).
Mentions: Previous studies have demonstrated that CXCR7 protein is specifically expressed in human breast cancer as opposed to normal breast tissue [27]. Therefore, our first step consisted in testing our staining protocol with the 11G8 antibody using a human tissue microarray that contained normal breast tissue and multiple breast carcinomas on the same slide. As expected, CXCR7 was expressed in most of the carcinomas but not in normal breast tissue. Two examples are reported in Figure 1 (A/D). This figure also shows the typical alterations of the glandular structure in the cancer tissue as compared to normal (counterstaining in 1B/E), higher magnification images of selected areas (square insets), and a negative control (1C).

Bottom Line: Furthermore, confocal microscopy and binding assays in cultured neurons show that CXCR7 protein is mainly located into cytoplasm, while little to no protein expression is found on neuronal plasma membrane.Interestingly, specific CXCR7 ligands that inhibit CXCL12 binding to CXCR7 do not alter CXCR4-activated survival signaling (pERK/pAkt) in rat cortical neurons.Overall, these results implicate CXCR4 as the main CXCL12 signaling receptor on the surface of differentiated neurons and suggest that CXCR7 may interact with CXCR4 at the intracellular level, possibly affecting CXCR4 trafficking and/or coupling to other proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT

Background: CXCR7 and CXCR4 are receptors for the chemokine CXCL12, which is involved in essential functions of the immune and nervous systems. Although CXCR7 transcripts are widely expressed throughout the central nervous system, little is known about its protein distribution and function in the adult brain. To evaluate its potential involvement in CXCL12/CXCR4 signaling in differentiated neurons, we studied CXCR7 protein expression in human brain and cultured neurons.

Methodology/principal findings: Immunohistochemistry and RT-PCR analyses of cortex and hippocampus from control and HIV-positive subjects provided the first evidence of CXCR7 protein expression in human adult neurons, under normal and pathological conditions. Furthermore, confocal microscopy and binding assays in cultured neurons show that CXCR7 protein is mainly located into cytoplasm, while little to no protein expression is found on neuronal plasma membrane. Interestingly, specific CXCR7 ligands that inhibit CXCL12 binding to CXCR7 do not alter CXCR4-activated survival signaling (pERK/pAkt) in rat cortical neurons. Neuronal CXCR7 co-localizes to some extent with the endoplasmic reticulum marker ERp29, but not with early/late endosome markers. Additionally, large areas of overlap are detected in the intracellular pattern of CXCR7 and CXCR4 expression.

Conclusions/significance: Overall, these results implicate CXCR4 as the main CXCL12 signaling receptor on the surface of differentiated neurons and suggest that CXCR7 may interact with CXCR4 at the intracellular level, possibly affecting CXCR4 trafficking and/or coupling to other proteins.

Show MeSH
Related in: MedlinePlus