Differences in expression of acetylcholinesterase and collagen Q control the distribution and oligomerization of the collagen-tailed forms in fast and slow muscles

The collagen-tailed forms of acetylcholinesterase (AChE) are accumulated at mammalian neuromuscular junctions. The A(4), A(8), and A(12) forms are exp ressed differently in the rat fast and slow muscles; the sternomastoid musc le contains essentially the A(12) form at end plates, whereas the soleus mu scle also contains extrajunctional A(4) and A(8) forms. We show that collag en Q (ColQ) transcripts become exclusively junctional in the adult sternoma stoid but remain uniformly expressed in the soleus. By coinjecting Xenopus oocytes with AChE(T) and ColQ mRNAs, we reproduced the muscle patterns of c ollagen-tailed forms. The soleus contains transcripts ColQ1 and ColQ1a, whe reas the sternomastoid only contains ColQ1a. Collagen-tailed AChE represent s the first evidence that synaptic components involved in cholinergic trans mission may be differently regulated in fast and slow muscles.