A unique role for clathrin light chain A in cell spreading and migration

Abstract

Clathrin heavy chain is the structural component of the clathrin triskelion, but unique functions for the two distinct and highly conserved clathrin light chains (CLCa and CLCb, also known as CLTA and CLTB, respectively) have been elusive. Here, we show that following detachment and replating, CLCa is uniquely responsible for promoting efficient cell spreading and migration. Selective depletion of CLCa, but not of CLCb, reduced the initial phase of isotropic spreading of HeLa, H1299 and HEK293 cells by 60-80% compared to siRNA controls, and wound closure and motility by ∼50%. Surface levels of β1-integrins were unaffected by CLCa depletion. However, CLCa was required for effective targeting of FAK (also known as PTK2) and paxillin to the adherent surface of spreading cells, for integrin-mediated activation of Src, FAK and paxillin, and for maturation of focal adhesions, but not their microtubule-based turnover. Depletion of CLCa also blocked the interaction of clathrin with the nucleation-promoting factor WAVE complex, and altered actin distribution. Furthermore, preferential recruitment of CLCa to budding protrusions was also observed. These results comprise the first identification of CLCa-specific functions, with implications for normal and neoplastic integrin-based signaling and cell migration.

Intracellular claudin‐1 at the invasive front of tongue squamous cell carcinoma is associated with lymph node metastasis

“…The molecular machineries required for clathrin‐dependent endocytosis are reportedly involved in the regulation of migration . As constitutive endocytosis of claudin‐1 was shown in SAS cells (Figure ), we examined the effects of endocytosis inhibitors (CPZ and IMP) on the migration of SAS cells.…”

“…A functional endosomal sorting complex required for transport (ESCRT) is involved in the constitutive recycling of claudin‐1 between the plasma membrane and intracellular vesicles in MDCK cells . Furthermore, there is growing evidence linking endocytosis and the regulation of cell migration . Thus, we hypothesized that a factor related to the membrane dynamics of claudin‐1 would be equivalent to the missing link between claudin‐1 and cancer metastasis.…”

Clathrin light chain diversity regulates membrane deformation in vitro and synaptic vesicle formation in vivo

“…8a). CLCa seems to have preferential connection with the actin cytoskeleton compared to CLCb 24,33 , which might further account for the ability of nCLCa clathrin to function on its own without nCLCb and benefit from involvement of accessory molecules. In the (normal) presence of nCLCb, the actin interactions of nCLCa may be "diluted down", so that the presence of nCLCb works as an attenuating balancing mechanism to control SV pools and neurotransmission by more efficient lattice formation, as opposed to using accessory factors.…”

“…Limited functional differences between CLCa and CLCb have been observed in cell culture with respect to clathrin dynamics 23 , during focal adhesion formation 24 and during cancer cell migration 25 , with mechanisms attributed to possible isoform-specific differences in CLC binding proteins and post-translational modification 26 . The capacity for biophysical differences in clathrin comprising different CLC isoforms and their splicing variants to influence tissue-specific clathrin functions has not yet been considered.…”

Membrane dynamics in cell migration

“…These distinctive structures are possible because of the assembly of approximately hundred clathrin triskelia (15). The clathrin triskelion is a highly evolutionary conserved structure (16), composed of three clathrin heavy chains (CHCs) and three clathrin light chains (CLCs) that radiate form a centre (13,16).…”