Mediator of receptor tyrosine kinase (RTK) signaling, and may act either downstream of MAPK or transduce signaling through a parallel branch of the RTK pathway (PubMed:11782402). Required for the development and organization of indirect flight muscle sarcomeres by regulating the formation of M line and H zone and the correct assembly of thick and thin filaments in the sarcomere (PubMed:26251439). May interact with Unc-89 (via protein kinase domain 1 or 2). In indirect flight muscle, more strongly associated with Z lines where it colocalizes with sls isoform A (kettin). Expressed ubiquitously in eye imaginal disk, slightly higher expression is seen in presumptive photoreceptors (PubMed:11782402). Expressed in indirect flight muscle (IFM) (at protein level) (PubMed:26251439). Flies exhibit compromised photoreceptor differentiation, cell survival and proliferation (PubMed:11782402). RNAi-mediated knockdown in muscles causes severe lethality at the early pupal stage and the few surviving animals cannot fly (PubMed:26251439). Severe defects in the indirect flight muscle structure characterized by narrower myofibrils and abnormal positioning of sarcomere Z line, M line and H line (PubMed:26251439). Although the spacing between Z line and M lines stays regular, M lines are not straight and sarcomere length is shorter. In the more affected myofibrils, the sarcomere structure is lost (PubMed:26251439). Localization of unc-89/obscurin to M lines and localization of kettin (sls isoform A) to Z line is not affected (PubMed:26251439). Truncated N-terminus.