western blot of insulin receptor - (Jun/19/2011 )

I did a western blot of the insulin receptor (Molecular weight: 95kDa) using Santa Cruz anti-insulin receptor antibody on a mammalian cell line (NIH 3T3). After developing the blot, I got two bands: one at 95kDa and other at ~ 45kDa. What could be the reason for the second band showing on my blot? Any help would be appreciated!!!

May be a nonspecific band, at the same time it could also be the specific one. specific in the sense, it might be the cleaved part of the receptor. As the job of the receptor when finished it has to be degraded or even the normal turn over might put them to lysosomal degradation and thereby the cleaved part might be the remaining part after being cut in the lysosome. or even some receptors undergo cleavage induced by MMPs, so this 45 KD part of insulin receptor might be the cleaved cytosolic part and the Extracellular part may shed into the medium.....these are just my assumptions, may be if you search into the literature you may get some more details.