Knockdown of TDP-43 in astrocytes induces immune activation
 
Thomas LaRocca¹, Andrea Mariani¹, Christopher D. Link^1
1Integrative Physiology, University of Colorado, Boulder, CO 80309 USA
 
TDP-43 is a multifunctional RNA binding protein directly implicated in the etiology of ALS.  We have previously shown that loss of TDP-43 in C. elegans, or knockdown of TDP-43 in human cell lines, leads to intracellular accumulation of double-stranded RNA (dsRNA)[1].  The disease-relevance of this dsRNA accumulation is unknown, although we have speculated that intracellular dsRNA accumulation could lead to innate immune activation, possibly contributing to the neuroinflammation observed in ALS.  To investigate this possibility, we have used siRNA transfection to knock down TDP-43 in primary rat astrocytes.  Using immunofluorescence, immunoblotting, and RNA-seq analysis, we find that TDP-43 knockdown leads to both increased intracellular dsRNA and expression of markers of astrocyte activation, including CD44 and LCN2.  Chemical inhibition of PKR, a dsRNA-activated kinase, blocks the expression of all activation markers assayed.  We suggest that intracellular accumulation of dsRNA may play a pathological role in ALS (and perhaps other neurodegenerative diseases), and that PKR inhibitors may have the potential to prevent reactive astrocytosis in ALS.
 
[1] Saldi TK, Ash PEA, Wilson G, Gonzales P, Garrido-Lecca A, Roberts CM, Dostal V, Gendron TF, Stein LD, Blumenthal T, Petrucelli L, Link CD.  (2014) TDP-1, the C. elegans ortholog of TDP-43, limits the accumulation of double-stranded RNA.  EMBO J   Dec 17;33(24):2947-66.