Conformations of tissue plasminogen activator (tPA) orchestrate neuronal survival by a crosstalk between EGFR and NMDAR

Abstract

Tissue-type plasminogen activator (tPA) is a pleiotropic serine protease of the central nervous system (CNS) with reported neurotrophic and neurotoxic functions. Produced and released under its single chain form (sc), the sc-tPA can be cleaved by plasmin or kallikrein in a two chain form, tc-tPA. Although both sc-tPA and tc-tPA display a similar fibrinolytic activity, we postulated here that these two conformations of tPA (sc-tPA and tc-tPA) could differentially control the effects of tPA on neuronal survival. Using primary cultures of mouse cortical neurons, our present study reveals that sc-tPA is the only one capable to promote N-methyl-D-aspartate receptor (NMDAR)-induced calcium influx and subsequent excitotoxicity. In contrast, both sc-tPA and tc-tPA are capable to activate epidermal growth factor receptors (EGFRs), a mechanism mediating the antiapoptotic effects of tPA. Interestingly, we revealed a tPA dependent crosstalk between EGFR and NMDAR in which a tPA-dependent activation of EGFRs leads to downregulation of NMDAR signaling and to subsequent neurotrophic effects.

Mutations in Vps15 perturb neuronal migration in mice and are associated with neurodevelopmental disease in humans

“…Antibodies targeting phosphoproteins were incubated with 1 mM sodium orthovanadate in 0.5% BSA/TBS. The following primary antibodies were used: 1:2,000 Vps15 for mouse studies (Novus Biologicals NBP1-30463) 39 , 1:1,000 VPS15 for human studies (Abcam ab124817, Abcam ab128903) 41 , 1:500 Vps34 (Cell Signaling, #3811) 42,43 , 1:1,000 Beclin1 (Cell Signaling #3738) 44 , 1:500 p62 (Novus Biologicals, H00008878-M01) 45 , 1:2,000 GAPDH (Millipore, MAB3 74) 26,46 , 1:1,000 ubiquitin (Santa Cruz, sc-8017) 47 , 1:10,000 α-tubulin (Sigma Aldrich, T6199) 48 , 1:100 LC3 (Nanotools, 0260-100/LC3-2G6) 49 , 1:600 EGFR (Cell Signaling #4267 S) 50 , 1:200 Nischarin (Santa Cruz, sc-365364) 21 , 1:500 PAK1 T423 (Cell Signaling, #2601 S) 51 and 1:500 N -terminal Vps15 antibody (Proteintech, 17894-1-AP). Western blots were quantified using ImageJ.…”

Tissue plasminogen activator promotes white matter integrity and functional recovery in a murine model of traumatic brain injury

“…CSPG has been implicated in the inhibition of spontaneous axonal plasticity after TBI (30,31). The neurotrophic effects of tPA are thought to be partly mediated by the epidermal growth factor receptor (EGFR) (32,33). As expected, CSPG decreased the length of tau + axons in neurons in a concentration-dependent manner (SI Appendix, Fig.…”

Tissue-Type Plasminogen Activator-A 296–299 Prevents Impairment of Cerebral Autoregulation After Stroke Through Lipoprotein-Related Receptor–Dependent Increase in cAMP and p38

“…33 Enhancement of NMDA-R signaling by tPA may depend on the type of neuron or the absence of astrocytes. 30–32 It is possible that activation of NMDA-R subunits within the synapse may support neuronal survival whereas high or sustained levels of activation of extrasynaptic NMDA-Rs may promote cell death. 34,35 This, in turn, may depend on the expression level or distribution of NR2A-D subunits that must interact with NR1 for NMDA-Rs to be functional.…”

“…The level and subcellular localization of wt-tPA may also help to determine whether it promotes cell death or survival via a plasminogen-independent proteolytic cleavage of an NR subunit 28 or non-proteolytic signaling through LRP via activation of mTOR, accumulation of HIF-1a, recruitment of glucose GLUT3 to the plasma membrane, and GLUT3-mediated uptake of glucose by neurons in the ischemic brain. 28,30 …”