Presynaptic active zones (AZ) contain many molecules essential for neurotransmitter release and are assembled in a highly organized manner. A network of adaptor proteins known as Cytomatrix at the AZ (CAZ), is important for shaping the structural characteristics of AZ. RIM-binding protein (RBP) family are binding partners of the CAZ protein RIM and also bind the voltage-gated calcium channels (VGCC) in mice and flies. Here, we investigated the physiological roles of RIMB-1, the homolog of RBPs in the nematode <i>C. elegans</i> RIMB-1 is expressed broadly in neurons and predominantly localized at presynaptic sites. Loss-of-function animals of <i>
rimb-1</i> displayed slight defects in motility and response to pharmacological inhibition of synaptic transmission, suggesting a modest involvement of <i>
rimb-1</i> in synapse function. We analyzed genetic interactions of <i>
rimb-1</i> by testing candidate genes and by an unbiased forward genetic screen for <i>
rimb-1</i> enhancer. Both analyses identified the RIM homolog UNC-10 that acts together with RIMB-1 to regulate presynaptic localization of the P/Q-type VGCC UNC-2/Ca<sub>v</sub>2. We also find that the precise localization of RIMB-1 to presynaptic sites requires presynaptic UNC-2/Ca<sub>v</sub>2. RIMB-1 has multiple FN3 and SH3 domains. Our transgenic rescue analysis with RIMB-1 deletion constructs revealed a functional requirement of a C-terminal SH3 in regulating UNC-2/Ca<sub>v</sub>2 localization. Together, these findings suggest a redundant role of RIMB-1/RBP and UNC-10/RIM to regulate the abundance of UNC-2/Ca<sub>v</sub>2 at the presynaptic AZ in <i>C. elegans</i>, depending on the bidirectional interplay between CAZ adapter and channel proteins.<b>SIGNIFICANCE STATEMENT</b>Presynaptic active zones (AZ) are highly organized structures for synaptic transmission with characteristic networks of adapter proteins called Cytomatrix at the AZ (CAZ). In this study, we characterized a CAZ protein RIMB-1, named for RIM-binding protein (RBP), in the nematode <i>C. elegans</i> Through systematic analyses of genetic interactions and an unbiased genetic enhancer screen of <i>
rimb-1</i>, we revealed a redundant role of two CAZ proteins RIMB-1/RBP and UNC-10/RIM in regulating presynaptic localization of UNC-2/Ca<sub>v</sub>2, a voltage-gated calcium channel (VGCC) critical for proper neurotransmitter release. Additionally, the precise localization of RIMB-1/RBP requires presynaptic UNC-2/Ca<sub>v</sub>2. These findings provide new mechanistic insight about how the interplay among multiple CAZ adapter proteins and VGCC contributes to the organization of presynaptic AZ.