Slit proteins are not dominant chemorepellents for olfactory tract and spinal motor axons

Abstract

Members of the Slit family are large extracellular glycoproteins that may function as chemorepellents in axon guidance and neuronal cell migration. Their actions are mediated through members of the Robo family that act as their receptors. In vertebrates, Slit causes chemorepulsion of embryonic olfactory tract, spinal motor, hippocampal and retinal ganglion cell axons. Since Slits are expressed in the septum and floor plate during the period when these tissues cause chemorepulsion of olfactory tract and spinal motor axons respectively, it has been proposed that Slits function as guidance cues. We have tested this hypothesis in collagen gel co-cultures using soluble Robo/Fc chimeras, as competitive inhibitors, to disrupt Slit interactions. We find that the addition of soluble Robo/Fc has no effect on chemorepulsion of olfactory tract and spinal motor axons when co-cultured with septum or floor plate respectively. Thus, we conclude that although Slits are expressed in the septum and floor plate, their proteins do not contribute to the major chemorepulsive activities emanating from these tissues which cause repulsion of olfactory tract and spinal motor axons.

The C-terminal fragment of axon guidance molecule Slit3 binds heparin and neutralizes heparin's anticoagulant activity

“…The 170-kDa band was in agreement with the predicted size of the full-length hSlit3 (167.7 kDa) and the 120-kDa band would correspond to the N-terminal fragment, suggesting that the cleavage of hSlit3 generates an 50-kDa C-terminal fragment. A similar cleavage occurred in hSlit2 and hSlit3 expressed in CHO cells (Patel et al 2001), and hSlit2 and dSlit expressed in COS and HEK 293 cells (Brose et al 1999). A putative cleavage site was proposed for hSlit2 (Brose et al 1999).…”

“…Expression of recombinant HSCF Slit3 has been observed to be cleaved to give rise to N-and C-terminal fragments in vivo (Patel et al 2001). We recently examined the biological function of a recombinant N-terminal fragment of hSlit3 and observed that the N-terminal fragment potently promotes angiogenesis (Zhang et al 2009), but the biological function of the C-terminal fragment has not been determined.…”

“…dSlit and bovine Slit2 were shown to be cleaved in vivo by unknown proteases (Brose et al 1999). In vitro cleavage was also reported for human Slit2 (hSlit2) and hSlit3 expressed in Chinese hasmster ovary (CHO) cells and for hSlit2 and dSlit expressed in COS and human embryonic kidney (HEK) 293 cells (Brose et al 1999;Patel et al 2001). Studies of mammalian Slit2 established that Slit2 binds through the second leucine-rich repeat to the appropriate receptors Robo to exert functions as a guidance molecule involved in neuron growth, cell migration and angiogenesis (Howitt et al 2004;Liu et al 2004;Morlot et al 2007;Hohenester 2008;Jones et al 2008).…”

Stromal Cell-SLIT3/Cardiomyocyte-ROBO1 Axis Regulates Pressure Overload-Induced Cardiac Hypertrophy

“…These in vitro data suggested that fibroblast and vascular mural cell–mediated SLIT3 can stimulate cardiomyocyte hypertrophy. As SLITs can be cleaved into N- and C-terminal fragments in vivo, 49 we next investigated which portion of SLIT3 was responsible for stimulating cardiomyocyte hypertrophy because these fragments have been determined to bind to different receptors. 26 , 30 We cultured NRCMs with recombinant N- and C-terminal fragments of SLIT3 (SLIT3-NT and SLIT3-CT, respectively) and observed that only SLIT3-NT could promote the transcription of Nppa and Nppb and stimulate NRCMs hypertrophy ( Figure S5K through S5M ).…”

Using Dictyostelium to Develop Therapeutics for Acute Respiratory Distress Syndrome

“…Slit guidance ligand 2 (Slit2), a chemoattractant or chemorepellent dependent on the isoform, and activation of Roundabout receptor (Robo1), a coreceptor of Slit2, induces chemorepulsion of axons as well as neutrophils (Hu, 1999;Nguyen Ba-Charvet et al, 1999;Park et al, 2016). Slit1 and Slit3 also induce chemorepulsion of olfactory tract and spinal motor axons during development (Patel et al, 2001).…”