PMC:3191169 / 19003-21661 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/3191169","sourcedb":"PMC","sourceid":"3191169","source_url":"http://www.ncbi.nlm.nih.gov/pmc/3191169","text":"Ephrin-As counteract BDNF signaling via suppression of ERK kinase activity\nNext, we investigated the underlying signaling mechanism, whereby ephrin-As and neurotrophins might interact. Focus was given on MAP kinases and especially ERK as a possible signaling mediator regulated by receptors of both guidance cues (see Introduction). Upon activation by ephrins, Eph receptors activate [49], [50], [51] or inactivate [46], [52], [53], [54], [55], [56] MAP kinases depending on e.g. cell type and Eph subclass implicated.\nFor these biochemical experiments requiring larger amounts of neuronal tissue, cortical neurons rather than hippocampal neurons were employed (Fig. 2). Both neuronal cell types behave identical in many parameters (ephrin-A5 induced growth cone collapse, ERK activation and e.g. BDNF-evoked gene expression; own data not shown). Therefore, data obtained should be interchangeable with both neuron types.\nShort-term activation of Eph forward signaling by ephrin-A5 application suppressed ERK kinase activation as revealed by decreased ERK1 and ERK2 phosphorylation (P-ERK). In agreement with our data, EphA activation also decreased ERK signaling in hippocampal neurons [46] and cortical neurons [55]. During longer exposure to ephrin-A5 (\u003e1h), P-ERK returned to control levels (Fig. 2A).\nApplication of BDNF alone expectedly increased P-ERK levels (Fig. 2B). Notably, when ephrin-A5 was co-applied with BDNF, ERK activity was reduced. This suggests that ephrin-A5 counteracted ERK activation by BDNF (Fig. 2B).\nOne way by which ephrin-A5 might inhibit ERK phosphorylation is recruitment of phosphatase activity, which has been implicated as downstream effector of an EphA mediated growth cone collapse [46]. Indeed, pre-incubation with various phosphatase inhibitors (i.e. okadaic acid, OA, blocking serine/threonine phosphatases; sodium vanadate, SV, a protein-tyrosine phosphatase inhibitor and a pan-phosphatase inhibitor coctail, mix) prevented ephrin-A5 from inhibiting ERK activity (Fig. 2C). EphA receptor phosphorylation assessed by P-EphA3 levels was not obviously altered by application of either phosphatase inhibitor (Fig. 2C and data not shown). We further analyzed whether ephrin-A5 also requires phosphatases to reduce BDNF-induced P-ERK levels (Fig. 2D; n = 3 independent experiments). In contrast to ephrin-A5 alone (Fig. 2C) we did not observe an major requirement of phosphatases to mediate this effect of ephrin-A5 on BDNF-mediated ERK phosphorylation (Fig. 2D). Only in the presence of the phosphatase inhibitor mix (mix) we observed a slight reconstitution of P-ERK levels comparable to BDNF treatment alone (Fig. 2D).","divisions":[{"label":"Title","span":{"begin":0,"end":74}}],"tracks":[{"project":"2_test","denotations":[{"id":"22022520-15145949-87377389","span":{"begin":385,"end":387},"obj":"15145949"},{"id":"22022520-19047466-87377390","span":{"begin":391,"end":393},"obj":"19047466"},{"id":"22022520-12925710-87377391","span":{"begin":397,"end":399},"obj":"12925710"},{"id":"22022520-18563700-87377392","span":{"begin":416,"end":418},"obj":"18563700"},{"id":"22022520-16522685-87377393","span":{"begin":422,"end":424},"obj":"16522685"},{"id":"22022520-11585923-87377394","span":{"begin":428,"end":430},"obj":"11585923"},{"id":"22022520-11331884-87377395","span":{"begin":434,"end":436},"obj":"11331884"},{"id":"22022520-20062052-87377396","span":{"begin":440,"end":442},"obj":"20062052"},{"id":"22022520-12486127-87377397","span":{"begin":446,"end":448},"obj":"12486127"},{"id":"22022520-18563700-87377398","span":{"begin":1188,"end":1190},"obj":"18563700"},{"id":"22022520-20062052-87377399","span":{"begin":1214,"end":1216},"obj":"20062052"},{"id":"22022520-18563700-87377400","span":{"begin":1721,"end":1723},"obj":"18563700"},{"id":"T49326","span":{"begin":385,"end":387},"obj":"15145949"},{"id":"T8546","span":{"begin":391,"end":393},"obj":"19047466"},{"id":"T48316","span":{"begin":397,"end":399},"obj":"12925710"},{"id":"T65025","span":{"begin":416,"end":418},"obj":"18563700"},{"id":"T31043","span":{"begin":422,"end":424},"obj":"16522685"},{"id":"T39133","span":{"begin":428,"end":430},"obj":"11585923"},{"id":"T69039","span":{"begin":434,"end":436},"obj":"11331884"},{"id":"T88714","span":{"begin":440,"end":442},"obj":"20062052"},{"id":"T78270","span":{"begin":446,"end":448},"obj":"12486127"},{"id":"T3503","span":{"begin":1188,"end":1190},"obj":"18563700"},{"id":"T68087","span":{"begin":1214,"end":1216},"obj":"20062052"},{"id":"T33975","span":{"begin":1721,"end":1723},"obj":"18563700"}],"attributes":[{"subj":"22022520-15145949-87377389","pred":"source","obj":"2_test"},{"subj":"22022520-19047466-87377390","pred":"source","obj":"2_test"},{"subj":"22022520-12925710-87377391","pred":"source","obj":"2_test"},{"subj":"22022520-18563700-87377392","pred":"source","obj":"2_test"},{"subj":"22022520-16522685-87377393","pred":"source","obj":"2_test"},{"subj":"22022520-11585923-87377394","pred":"source","obj":"2_test"},{"subj":"22022520-11331884-87377395","pred":"source","obj":"2_test"},{"subj":"22022520-20062052-87377396","pred":"source","obj":"2_test"},{"subj":"22022520-12486127-87377397","pred":"source","obj":"2_test"},{"subj":"22022520-18563700-87377398","pred":"source","obj":"2_test"},{"subj":"22022520-20062052-87377399","pred":"source","obj":"2_test"},{"subj":"22022520-18563700-87377400","pred":"source","obj":"2_test"},{"subj":"T49326","pred":"source","obj":"2_test"},{"subj":"T8546","pred":"source","obj":"2_test"},{"subj":"T48316","pred":"source","obj":"2_test"},{"subj":"T65025","pred":"source","obj":"2_test"},{"subj":"T31043","pred":"source","obj":"2_test"},{"subj":"T39133","pred":"source","obj":"2_test"},{"subj":"T69039","pred":"source","obj":"2_test"},{"subj":"T88714","pred":"source","obj":"2_test"},{"subj":"T78270","pred":"source","obj":"2_test"},{"subj":"T3503","pred":"source","obj":"2_test"},{"subj":"T68087","pred":"source","obj":"2_test"},{"subj":"T33975","pred":"source","obj":"2_test"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"2_test","color":"#93ec9e","default":true}]}]}}