IRS1 and IRS2 are {HEAD ~ part} of the insulin or {TAIL ~ insulin} like growth factor signaling pathway 
IRS1 and IRS2 are { HEAD ~ part } of the insulin or { TAIL ~ insulin } like growth factor signaling pathway
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH