Cooperative activities of dICA69 N-BAR and dCIP4 F-BAR domain proteins regulate membrane tubule organization in vivo

Intracellular membrane tubules play a crucial role in diverse cellular processes, and their regulation is facilitated by Bin-Amphiphysin-Rvs (BAR) domain-containing proteins. This study investigates the roles of dICA69N-BAR and dCIP4F-BAR in vivo, focusing on their impact on in vivo tubule organization. Through cell culture and immunofluorescence staining, we observed co-localization of endogenous dICA69 with dCIP4-induced membrane tubules, indicating their potential recruitment for tubule formation and maintenance. Additionally, dCIP4-positive tubules exhibit enrichment of actin regulatory proteins such as Wasp, SCAR, Arp2, Arp3, and Syndapin. Overexpressing dICA69N-BAR in S2R+ cells reveals distinct punctate patterns in the perinuclear region. An earlier study indicated that F-BAR proteins spontaneously segregate from the N-BAR domain-containing proteins during membrane tubule formation. In contrast, our observation supports a model in which different BAR-domain family members can associate with the same tubule and cooperate to fine-tune the tubule width. Moreover, our analysis highlights how dCIP4F-BAR facilitates the redistribution of dICA69N-BAR punctae, leading to altered patterns within the cells. These cooperative activities of dICA69N-BAR and dCIP4F-BAR are vital for the precise organization of intracellular tubules. Understanding the underlying mechanisms governing this cooperation provides valuable insights into cellular dynamics and the organization of membrane tubules. The implications extend to various physiological and pathological conditions related to intracellular membrane dynamics.