SHC2

SHC2 (ShcB/Sck) is a phosphotyrosine adapter protein that couples activated receptor tyrosine kinases to downstream MAPK signaling and governs neuronal survival and function (PMID:12006576, PMID:11163269). It engages receptors through two distinct modular interfaces: its SH2 domain binds the VEGF receptor KDR/VEGFR2 at phosphotyrosine-1175 in a phosphorylation-dependent manner upon VEGF stimulation in endothelial cells, while its PTB domain binds Trk receptors (TrkA at Y499, TrkB at Y515) following neurotrophin stimulation (PMID:10749680, PMID:12006576). Receptor engagement drives SHC2 tyrosine phosphorylation and enhances MAPK activation, and dominant-negative SH2 chimeras attenuate VEGF-induced MAPK signaling (PMID:10749680, PMID:12006576). In the nervous system, SHC2 is required for survival and maturation of nociceptive sensory neurons and, redundantly with ShcC, for sympathetic neuron development (PMID:11163269). In cerebellar Purkinje cells it maintains ER Ca2+ store content and SERCA activity, an activity required for synaptic long-term depression and cerebellar motor function, as shown by knockout phenotypes rescued by ShcB re-expression (PMID:32879382). SHC2 also acts as a required downstream effector in disease contexts, mediating CD95-driven cell cycle progression and metastasis in pancreatic adenocarcinoma and TrkB-driven angiogenic responses in chondrocytes (PMID:25613377, PMID:34107348).

1. 1998 High

   Established that SHC2 is a receptor-specific adapter by defining its physical link to the VEGF receptor and mapping the interaction interface, answering how SHC2 connects to receptor tyrosine kinases.

   Evidence Yeast two-hybrid with KDR cytoplasmic domain, site-directed mutagenesis, and SH2/PTB deletion constructs

   PMID:10749680 PMID:9790910

   Open questions at the time

   • Did not establish downstream signaling consequences
   • Functional role in endothelial cells not yet tested
2. 1998 Medium

   Distinguished SHC2 from the related neuronal adapter N-Shc, showing SHC2 has a unique binding partner (a 135 kDa phosphoprotein) and distinct kinase relationships, establishing functional non-redundancy among Shc family members.

   Evidence Immunoprecipitation in neuronal cells with NGF/BDNF stimulation and v-Src co-expression

   PMID:9507002

   Open questions at the time

   • Identity of the 135 kDa phosphoprotein unresolved
   • Single-lab Co-IP without reciprocal validation
3. 2000 High

   Confirmed in physiological endothelial cells that the SHC2-KDR interaction occurs at Y1175 and contributes functionally to VEGF signaling, moving the interaction from yeast two-hybrid to native receptor signaling.

   Evidence Co-IP from VEGF-stimulated PAE cells, recombinant SH2-phosphopeptide binding, and dominant-negative chimera experiments

   PMID:10749680

   Open questions at the time

   • Downstream effectors recruited by SHC2 at KDR not identified
   • MAPK attenuation shown only with artificial chimera
4. 2000 High

   Defined the in vivo neuronal requirement for SHC2, answering whether the adapter is essential for development by revealing nociceptive neuron loss and redundancy with ShcC in sympathetic neurons.

   Evidence Single and double ShcB/ShcC knockout mice with histological analysis of peripheral neurons

   PMID:11163269

   Open questions at the time

   • Receptor and signaling pathway driving the survival defect not yet linked
   • Molecular mechanism of survival support unresolved
5. 2001 Medium

   Refined SHC2 biochemistry by showing the full-length p68 isoform is the efficiently phosphorylated form and that its SH2-mediated pp135 interaction is Src-dependent and depolarization-regulated.

   Evidence Genomic organization analysis, EGF-induced phosphorylation Western blots, SH2 Co-IP with Src inhibitor treatment

   PMID:11409899

   Open questions at the time

   • pp135 identity remains unknown
   • Functional consequence of the depolarization-dependent interaction untested
6. 2002 High

   Connected SHC2's neuronal role to a specific receptor class, showing PTB-domain binding to Trk receptors at defined phosphotyrosines drives neurotrophin-stimulated MAPK activation in primary neurons.

   Evidence Co-IP in Trk-expressing cells and primary cortical neurons, phosphotyrosine-dependent binding, and MAPK activation assays

   PMID:12006576

   Open questions at the time

   • Link between Trk binding and the in vivo neuronal survival phenotype not directly demonstrated
   • Downstream effectors beyond MAPK not mapped
7. 2002 High

   Solidified SHC2 expression in vascular endothelium and its VEGF-induced recruitment to KDR Y1175, integrating expression, localization, and signaling for the endothelial arm.

   Evidence RT-PCR, Western blot, immunohistochemistry, and Co-IP from VEGF-treated HUVEC and PAE cells

   PMID:12214271

   Open questions at the time

   • Specific endothelial functional output of SHC2 signaling not quantified
   • Downstream adapters recruited by SHC2 unresolved
8. 2015 Medium

   Extended SHC2 into disease biology by placing it as an indispensable downstream mediator of CD95-driven cell cycle progression and metastasis in pancreatic cancer.

   Evidence In silico RNA profiling, PDAC cancer stem cell and xenograft/syngeneic models, and pharmacological CD95 inhibition

   PMID:25613377

   Open questions at the time

   • Biochemical mechanism linking SHC2 to cell cycle progression not defined
   • Direct CD95-SHC2 physical interaction not shown
9. 2020 High

   Revealed an unexpected non-canonical role for SHC2 in cerebellar Purkinje cells, where it maintains ER Ca2+ stores via SERCA activity to enable long-term depression, established causally by rescue.

   Evidence ShcB knockout mice with behavior, cerebellar LTD electrophysiology, Ca2+ imaging, SERCA assay, and re-expression rescue

   PMID:32879382

   Open questions at the time

   • Molecular link between adapter function and SERCA regulation unknown
   • Whether this role requires receptor tyrosine kinase input untested
10. 2021 Medium

    Placed SHC2 as a required downstream effector of TrkB in chondrocytes, showing it transmits TrkB-driven migration, angiogenesis, and VEGF secretion signals.

    Evidence shRNA knockdown and overexpression epistasis in IL-1β-stimulated chondrocytes with functional and VEGF ELISA readouts

    PMID:34107348

    Open questions at the time

    • Direct TrkB-SHC2 interaction in chondrocytes not biochemically shown
    • Single-lab cell-line epistasis without in vivo confirmation

• The molecular identity of the SHC2-specific pp135 partner and the biochemical mechanism by which SHC2 controls SERCA activity and cell cycle progression remain unresolved.
• pp135 has not been identified
• No mechanistic link between SHC2 adapter function and SERCA/ER Ca2+ regulation
• No structural model of SHC2 receptor complexes