BPAG1n4 is essential for retrograde axonal transport in sensory neurons

Liu JJ, Ding J, Kowal AS, Nardine T, Allen E, Delcroix JD, Wu C, Mobley W, Fuchs E and Yang Y
Source: J Cell Biol
Publication Date: (2003)
Issue: 163(2): 223-229
Cells used in publication:
Dorsal root ganglion (DRG), mouse
Species: mouse
Tissue Origin: brain
Sensory neurodegeneration occurs in mice defective in BPAG1 (bullous pemphigoid antigen 1), a gene encoding cytoskeletal linker proteins capable of anchoring neuronal intermediate filaments to actin cytoskeleton. The authors characterized the functions of a novel BPAG1 neuronal isoform, BPAG1n4 and its role in retrograde axonal transport in sensory neurons. BPAG1n4 contains a ERM (ezrin/radixin/moesin) domain interacting with dynactin. Mouse DRG neurons were nucleofected with an ERM-GFP or GFP expression plasmids. To examine retrograde transport, the neurons were incubated with media containing the tracer transferrin conjugated with Texas red (Tf-TR). The media were replaced with tracer free media and retrograde transport of Tf-TR was monitored at 2-h time points. ERM-GFP transfected neurons failed to transport Tf-TR retrogradely demonstrating that the isolated ERM is sufficient to disrupt BPAG1n4?s function in sensory neurons in a dominant-negative fashion.
Disruption of the BPAG1 (bullous pemphigoid antigen 1) gene results in progressive deterioration in motor function and devastating sensory neurodegeneration in the null mice. We have previously demonstrated that BPAG1n1 and BPAG1n3 play important roles in organizing cytoskeletal networks in vivo. Here, we characterize functions of a novel BPAG1 neuronal isoform, BPAG1n4. Results obtained from yeast two-hybrid screening, blot overlay binding assays, and coimmunoprecipitations demonstrate that BPAG1n4 interacts directly with dynactin p150Glued through its unique ezrin/radixin/moesin domain. Studies using double immunofluorescent microscopy and ultrastructural analysis reveal physiological colocalization of BPAG1n4 with dynactin/dynein. Disruption of the interaction between BPAG1n4 and dynactin results in severe defects in retrograde axonal transport. We conclude that BPAG1n4 plays an essential role in retrograde axonal transport in sensory neurons. These findings might advance our understanding of pathogenesis of axonal degeneration and neuronal death.