Death-associated protein kinase, DAPK, is a Ca2+/calmodulin-regulated Ser/Thr kinase that promotes anti-adhesion and cell death. Although the multiple physiological functions of DAPK are demonstrated, its intracellular signaling mechanism is largely unknown. To get insight into DAPK molecular signaling network, our laboratory searched for its interacting protein and identified leukocyte common antigen related tyrosine phosphatase (LAR) as one of its interacting partner. The first part of this thesis focused on studying their physical interaction. DAPK interacts with LAR in vivo through its ankyrin repeat domain, of which 3-6 repeats are both sufficient and required for interacting with LAR. On the other hand, the association of LAR and DAPK ankyrin repeats is mediated by LAR phosphatase domain, D1 or D2, as well as both of them. For the latter part of the thesis, we aimed to identify the possible antagonist of LAR, which was demonstrated in our laboratory as a DAPK activator through its dephosphorylation of DAPK at Y491/492 residues. It was discovered that there exists certain adhesion-dependent tyrosine kinase phosphorylating DAPK at Y491/492. Subsequent experiments identified this kinase as Src. By making use of Src/Fyn/Yes-triple knockout cell, we evaluated the determinant role for Src to regulate DAPK tyrosine phosphorylation at both exogenous and endogenous levels. The in vivo interaction between DAPK and Src is demonstrated. We also showed that the Y491/492 residues are the major sites for DAPK phosphorylation by Src. To investigate if this Src-mediated DAPK phosphorylation is of functional significance, we performed in vitro DAPK kinase assay and found that Src expression could inhibit DAPK catalytic activity. Therefore, it is through the direct tyrosine phosphorylation of DAPK Y491/492 that Src inhibits DAPK catalytic activity. In conclusion, Src is identified as DAPK inhibitor acting in a reverse direction in regard to LAR, revealing the reciprocal regulation of DAPK by a pair of tyrosine kinase and phosphatase, Src and LAR.