The Interplay Between SEPT9 and EPLIN Regulates Adhesion and Migration of Human Fibroblasts

Core Concepts

The septin protein SEPT9 and the actin-binding protein EPLIN cooperatively regulate the adhesion and migration of human fibroblasts through their direct interaction and coordination of the actin cytoskeleton.

Abstract

The content describes the interplay between the septin protein SEPT9 and the actin-binding protein EPLIN in regulating the adhesion and migration of human fibroblasts. Key highlights: SEPT9 directly interacts with the LIM domain of EPLIN in a zinc-dependent manner. The expression levels of SEPT9 positively correlate with cell motility, where SEPT9 overexpression enhances migration and SEPT9 knockout severely impairs it. EPLIN overexpression can partially rescue the migration defect in SEPT9 knockout cells, suggesting their cooperative regulation of cell migration. SEPT9 and EPLIN co-regulate the organization of the actin cytoskeleton, with SEPT9 promoting actin bundling and EPLIN influencing the distribution of actin filaments. The size and localization of focal adhesions are dependent on the expression levels of SEPT9 and EPLIN, with SEPT9 playing a more dominant role. The interaction between SEPT9 and EPLIN is crucial for the proper formation and dynamics of cell protrusions during migration. Overall, the content demonstrates that the interplay between SEPT9 and EPLIN is an important mechanism regulating cell adhesion and migration through their coordinated effects on the actin cytoskeleton and focal adhesions.

Stats

The mean square displacement (MSD) of 1306 cells increases upon SEPT9 overexpression and decreases upon SEPT9 knockout. The velocity of cell movement is significantly enhanced upon SEPT9 overexpression and significantly reduced upon SEPT9 knockout. SEPT9 overexpression enhances cell migration by 1.4-fold, while SEPT9 knockout reduces migration by 8-fold. EPLIN knockdown increases cell migration by 3-fold, while EPLIN overexpression has a mild 1.15-fold increase. The initiation of cell-surface attachment is reduced by 40% in SEPT9 overexpression and prolonged by 320% in SEPT9 knockout. The size of focal adhesions increases by 32% in SEPT9 overexpression and decreases by 43% in SEPT9 knockout.

Quotes

"The low motility of SEPT9-depleted cells could be partly rescued by increased levels of EPLIN." "Increased levels of SEPT9 and EPLIN enhanced the size of focal adhesions in cell protrusions, correlating with a stabilization of actin bundles, whereas decreased levels have the opposite effect." "Our work thus establishes the interaction between SEPT9 and Eplin as important link between the septin and the actin cytoskeleton that influences cell adhesion and motility."

Key Insights Distilled From

The concerted action of SEPT9 and EPLIN modulates the adhesion and migration of human fibroblasts

by Hecht,M., Ma... at www.biorxiv.org 08-09-2022

https://www.biorxiv.org/content/10.1101/2022.08.08.503265v1

Deeper Inquiries

How might the SEPT9-EPLIN interaction be regulated in response to different extracellular cues or mechanical stimuli to modulate cell adhesion and migration

The SEPT9-EPLIN interaction could be regulated in response to different extracellular cues or mechanical stimuli through various mechanisms. One possible regulatory mechanism is post-translational modifications (PTMs) of SEPT9 and EPLIN in response to specific signals. For example, phosphorylation of SEPT9 or EPLIN by kinases activated by extracellular signals could alter their interaction or localization. Additionally, changes in the expression levels of SEPT9 or EPLIN in response to external stimuli could impact their interaction dynamics. Moreover, the cellular localization of SEPT9 and EPLIN could be regulated by extracellular cues. For instance, signaling pathways activated by mechanical stimuli or growth factors could influence the subcellular localization of SEPT9 and EPLIN, leading to changes in their interaction at specific cellular locations. Furthermore, the binding affinity between SEPT9 and EPLIN could be modulated by the presence of other proteins or cofactors that are regulated by external signals. These proteins may act as mediators or regulators of the SEPT9-EPLIN interaction in response to different extracellular cues or mechanical stimuli.

What other cytoskeletal or signaling proteins might be involved in the SEPT9-EPLIN mediated regulation of the actin cytoskeleton and focal adhesions

The SEPT9-EPLIN mediated regulation of the actin cytoskeleton and focal adhesions likely involves interactions with other cytoskeletal or signaling proteins. One potential player in this regulatory network is the Arp2/3 complex, which is known to be involved in actin branching and dynamics. EPLIN has been shown to interact with the Arp2/3 complex to regulate actin dynamics, and the SEPT9-EPLIN axis may modulate the activity of the Arp2/3 complex in the context of cell migration and adhesion. Additionally, other septins such as SEPT2, SEPT6, and SEPT7, which are part of the septin hetero-octamer along with SEPT9, may also play a role in the regulation of the actin cytoskeleton and focal adhesions. These septins are known to interact with actin filaments and contribute to cytoskeletal organization. The interplay between different septins and EPLIN could further modulate actin dynamics and focal adhesion formation. Furthermore, signaling proteins such as focal adhesion kinase (FAK) and integrins, which are key regulators of focal adhesion dynamics, may interact with the SEPT9-EPLIN complex to coordinate cell adhesion and migration processes. The crosstalk between these signaling proteins and the SEPT9-EPLIN axis could fine-tune the regulation of the actin cytoskeleton and focal adhesions in response to various stimuli.

Could the SEPT9-EPLIN axis be a potential therapeutic target for diseases involving aberrant cell migration, such as cancer metastasis or inflammatory disorders

The SEPT9-EPLIN axis could indeed be a potential therapeutic target for diseases involving aberrant cell migration, such as cancer metastasis or inflammatory disorders. Targeting this axis could offer a way to modulate cell adhesion and migration processes, which are critical for the progression of these diseases. In cancer metastasis, dysregulated cell migration plays a key role in the spread of cancer cells to distant sites. By targeting the SEPT9-EPLIN interaction, it may be possible to inhibit the formation of focal adhesions and actin structures that are essential for cancer cell migration. This could potentially impede the metastatic spread of cancer cells and limit disease progression. In inflammatory disorders, excessive cell migration and adhesion can contribute to tissue damage and inflammation. Modulating the SEPT9-EPLIN axis could help regulate the inflammatory response by controlling the migration of immune cells to inflamed tissues. By targeting this axis, it may be possible to reduce excessive cell migration and adhesion, thereby mitigating the inflammatory process. Overall, targeting the SEPT9-EPLIN axis could offer a novel therapeutic approach for diseases characterized by aberrant cell migration, providing a potential strategy to intervene in the pathological processes associated with these conditions.