Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C.
Using permeabilized gonadotropes, we examined whether Ca2(+)-stimulated luteinizing-hormone (LH) exocytosis is mediated by the Ca2(+)-activated phospholipid-dependent protein kinase (protein kinase C). In the presence of high [Ca2+]free (pCa 5), alpha-toxin-permeabilized sheep gonadotropes secrete a...
| Main Authors: | , , |
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| Format: | Journal article |
| Jezik: | English |
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1990
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| _version_ | 1826261108607942656 |
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| author | Van Der Merwe, P Millar, R Davidson, J |
| author_facet | Van Der Merwe, P Millar, R Davidson, J |
| author_sort | Van Der Merwe, P |
| collection | OXFORD |
| description | Using permeabilized gonadotropes, we examined whether Ca2(+)-stimulated luteinizing-hormone (LH) exocytosis is mediated by the Ca2(+)-activated phospholipid-dependent protein kinase (protein kinase C). In the presence of high [Ca2+]free (pCa 5), alpha-toxin-permeabilized sheep gonadotropes secrete a burst of LH and then become refractory to maintained high [Ca2+]free. The protein kinase C activator phorbol myristate acetate (PMA) is able to stimulate further LH release from cells made refractory to high [Ca2+]free, suggesting that Ca2+ does not stimulate LH release by activating protein kinase C. Staurosporine, a protein kinase C inhibitor, inhibited PMA-stimulated (50% inhibition at 20 nM), but not Ca2(+)-stimulated, LH exocytosis. In cells desensitized to PMA by prolonged exposure to a high PMA concentration, Ca2(+)-stimulated LH exocytosis (when corrected for depletion of total cellular LH) was not inhibited. Ba2+ was able to stimulate LH exocytosis to a maximal extent similar to Ca2+, although higher Ba2+ concentrations were necessary. Ba2+ and Ca2+ stimulated LH exocytosis with a similar time course, and both were inhibitory at high concentrations. Furthermore, cells made refractory to Ca2+ were also refractory to Ba2+. These data strongly suggest that Ba2+ and Ca2+ act through the same mechanism. Since Ba2+ is a poor activator of protein kinase C, these findings are additional evidence against a major role for protein kinase C in mediating Ca2(+)-stimulated LH exocytosis. |
| first_indexed | 2024-03-06T19:16:24Z |
| format | Journal article |
| id | oxford-uuid:188955af-5452-4bf5-a05e-0469b7b0619e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T19:16:24Z |
| publishDate | 1990 |
| record_format | dspace |
| spelling | oxford-uuid:188955af-5452-4bf5-a05e-0469b7b0619e2022-03-26T10:43:45ZCalcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:188955af-5452-4bf5-a05e-0469b7b0619eEnglishSymplectic Elements at Oxford1990Van Der Merwe, PMillar, RDavidson, JUsing permeabilized gonadotropes, we examined whether Ca2(+)-stimulated luteinizing-hormone (LH) exocytosis is mediated by the Ca2(+)-activated phospholipid-dependent protein kinase (protein kinase C). In the presence of high [Ca2+]free (pCa 5), alpha-toxin-permeabilized sheep gonadotropes secrete a burst of LH and then become refractory to maintained high [Ca2+]free. The protein kinase C activator phorbol myristate acetate (PMA) is able to stimulate further LH release from cells made refractory to high [Ca2+]free, suggesting that Ca2+ does not stimulate LH release by activating protein kinase C. Staurosporine, a protein kinase C inhibitor, inhibited PMA-stimulated (50% inhibition at 20 nM), but not Ca2(+)-stimulated, LH exocytosis. In cells desensitized to PMA by prolonged exposure to a high PMA concentration, Ca2(+)-stimulated LH exocytosis (when corrected for depletion of total cellular LH) was not inhibited. Ba2+ was able to stimulate LH exocytosis to a maximal extent similar to Ca2+, although higher Ba2+ concentrations were necessary. Ba2+ and Ca2+ stimulated LH exocytosis with a similar time course, and both were inhibitory at high concentrations. Furthermore, cells made refractory to Ca2+ were also refractory to Ba2+. These data strongly suggest that Ba2+ and Ca2+ act through the same mechanism. Since Ba2+ is a poor activator of protein kinase C, these findings are additional evidence against a major role for protein kinase C in mediating Ca2(+)-stimulated LH exocytosis. |
| spellingShingle | Van Der Merwe, P Millar, R Davidson, J Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title | Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title_full | Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title_fullStr | Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title_full_unstemmed | Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title_short | Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. |
| title_sort | calcium stimulates luteinizing hormone lutropin exocytosis by a mechanism independent of protein kinase c |
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