Biology subjects

Kulasekaran, G.

Publications and source records attributed to Kulasekaran, G..

3 recordsLinked to original sources

bioRxiv2023

DENND6A couples Arl8b to a Rab34/RILP/dynein complex regulating retrograde lysosomal trafficking and autophagy

Lysosomes help maintain cellular proteostasis, and defects in lysosomal positioning and function lead to diseases including neurodegenerative disorders. The spatiotemporal distribution of lysosomes is regulated by small GTPases, including Rabs, which are activated by guanine nucleotide exchange factors (GEFs). DENN domain-bearing proteins are the largest family of Rab GEFs. Using a cell-based assay, we screened the DENN domain protein family member DENND6A for potential GEF activity toward all 60 Rabs and identified 20 potential DENND6A substrates, including Rab34. Here, we demonstrate that DENND6A activates Rab34, which recruits a RILP/dynein complex to the lysosomes, promoting lysosomal retrograde trafficking from the cell periphery to the minus ends of microtubules. Further, we identify DENND6A as an effector of Arl8b, a major regulatory GTPase on lysosomes. Initially known for promoting anterograde transport of lysosomes, Arl8b also facilitates lysosomal retrograde transport. We demonstrate that Arl8b recruits DENND6A to peripheral lysosomes to activate Rab34 and initiate retrograde transport, regulating nutrient-dependent lysosomal juxtanuclear repositioning and loss of DENND6A impairs autophagic flux. Our findings support a model whereby Arl8b/DENND6A/Rab34-dependent lysosomal retrograde trafficking controls autophagy.

cell biology↗

bioRxiv2023

DENND2B activates Rab35 at the intercellular bridge regulating cytokinetic abscission and tetraploidy

Cytokinesis is the final stage of cell division. Successful cytokinesis requires membrane trafficking pathways regulated by Rabs, molecular switches activated by guanine nucleotide exchange factors (GEFs). Late in cytokinesis, an intercellular cytokinetic bridge (ICB) connecting the two daughter cells undergoes abscission, which requires depolymerization of actin. Rab35 recruits MICAL1 to oxidate and depolymerize actin filaments. We report that DENND2B, a protein previously implicated in cancer, mental retardation and multiple congenital disorders functions as a GEF for Rab35 and recruits and activates the GTPase at the ICB. Unexpectedly, the N-terminal region of DENND2B interacts with an active mutant of Rab35, suggesting that DENND2B is both a Rab35 GEF and effector. Knockdown of DENND2B delays abscission resulting in increased multinucleated cells and overaccumulation of F-actin at the ICB. F-actin accumulation leads to formation of a chromatin bridge, a process known to activate the NoCut/abscission checkpoint, and DENND2B knockdown actives Aurora B kinase, a hallmark of checkpoint activation. This study identifies DENND2B as a crucial player in cytokinetic abscission and provides insight into the multisystem disorder associated with DENND2B mutation.

cell biology↗

bioRxiv2020

An Arf/Rab cascade controls the growth and invasiveness of glioblastoma

Glioblastoma is the most common and deadly malignant brain cancer. We now demonstrate that loss of function of the endosomal GTPase Rab35 in human brain tumor initiating cells (BTICs) increases glioblastoma growth and decreases animal survival following BTIC implantation in mouse brain. Mechanistically, we identify that the GTPase Arf5 interacts with the guanine nucleotide exchange factor (GEF) for Rab35, DENND1/connecdenn and allosterically enhances its GEF activity towards Rab35. Knockdown of either Rab35 or Arf5 increases cell migration, invasiveness and self-renewal in culture and enhances the growth and invasiveness of BTIC-initiated brain tumors in mice. RNAseq of the tumors reveals upregulation of the tumor-promoting transcription factor SPOCD1, and disruption of the Arf5/Rab35 axis in glioblastoma cells leads to strong activation of the epidermal growth factor receptor with resulting enhancement of SPOCD1 levels. These discoveries reveal an unexpected cascade between an Arf and a Rab and indicate a role for the cascade, and thus endosomal trafficking, in brain tumors.

cancer biology↗