Protein interaction networks are a system of proteins that have physical contact during specific biochemical processes. Virtually every biological process will involve these protein-protein interactions.
Above is a PTK7 protein interaction network created using the String database. Red indicates the Biological Process: Wnt/PCP Pathway. Blue indicates the Molecular Function: Coreceptor Activity.
Conclusion
The proteins labeled in red are involved in the Wnt/PCP pathway. These include PTK7, WNT5A, and the disheveled (DVL) proteins just to name a few of the many proteins involved. The proteins labeled in blue are involved with coreceptor activity. LRP6 is of particular interest because it is known to be involved in bone development and it is regulated by PTK7.